fix flag spacing in README

`--source-map-include-sources` makes the column width too wide.  Adding spacing helps makes it more readable.

README.md

@@ -54,22 +54,29 @@ The available options are:
 ```
   --source-map                  Specify an output file where to generate source
                                 map.
+
   --source-map-root             The path to the original source to be included
                                 in the source map.
+
   --source-map-url              The path to the source map to be added in //#
                                 sourceMappingURL.  Defaults to the value passed
                                 with --source-map.
+
   --source-map-include-sources  Pass this flag if you want to include the
                                 content of source files in the source map as
                                 sourcesContent property.
+                                
   --in-source-map               Input source map, useful if you're compressing
                                 JS that was generated from some other original
                                 code.
+
   --screw-ie8                   Pass this flag if you don't care about full
                                 compliance with Internet Explorer 6-8 quirks
                                 (by default UglifyJS will try to be IE-proof).
+
   --expr                        Parse a single expression, rather than a
                                 program (for parsing JSON)
+
   -p, --prefix                  Skip prefix for original filenames that appear
                                 in source maps. For example -p 3 will drop 3
                                 directories from file names and ensure they are
@@ -77,18 +84,26 @@ The available options are:
                                 relative, which will make UglifyJS figure out
                                 itself the relative paths between original
                                 sources, the source map and the output file.
+
   -o, --output                  Output file (default STDOUT).
+
   -b, --beautify                Beautify output/specify output options.
+
   -m, --mangle                  Mangle names/pass mangler options.
+
   -r, --reserved                Reserved names to exclude from mangling.
+
   -c, --compress                Enable compressor/pass compressor options. Pass
                                 options like -c
                                 hoist_vars=false,if_return=false. Use -c with
                                 no argument to use the default compression
                                 options.
+
   -d, --define                  Global definitions
+
   -e, --enclose                 Embed everything in a big function, with a
                                 configurable parameter/argument list.
+
   --comments                    Preserve copyright comments in the output. By
                                 default this works like Google Closure, keeping
                                 JSDoc-style comments that contain "@license" or
@@ -101,37 +116,54 @@ The available options are:
                                 kept when compression is on, because of dead
                                 code removal or cascading statements into
                                 sequences.
+
   --preamble                    Preamble to prepend to the output.  You can use
                                 this to insert a comment, for example for
                                 licensing information.  This will not be
                                 parsed, but the source map will adjust for its
                                 presence.
+
   --stats                       Display operations run time on STDERR.
+
   --acorn                       Use Acorn for parsing.
+
   --spidermonkey                Assume input files are SpiderMonkey AST format
                                 (as JSON).
+
   --self                        Build itself (UglifyJS2) as a library (implies
                                 --wrap=UglifyJS --export-all)
+
   --wrap                        Embed everything in a big function, making the
                                 “exports” and “global” variables available. You
                                 need to pass an argument to this option to
                                 specify the name that your module will take
                                 when included in, say, a browser.
+
   --export-all                  Only used when --wrap, this tells UglifyJS to
                                 add code to automatically export all globals.
+
   --lint                        Display some scope warnings
+
   -v, --verbose                 Verbose
+
   -V, --version                 Print version number and exit.
+
   --noerr                       Don't throw an error for unknown options in -c,
                                 -b or -m.
+
   --bare-returns                Allow return outside of functions.  Useful when
                                 minifying CommonJS modules.
+
   --keep-fnames                 Do not mangle/drop function names.  Useful for
                                 code relying on Function.prototype.name.
+
   --reserved-file               File containing reserved names
+
   --reserve-domprops            Make (most?) DOM properties reserved for
                                 --mangle-props
+
   --mangle-props                Mangle property names
+
   --name-cache                  File to hold mangled names mappings
 ```