Added separator option

[manuelbieh]

I had one really annoying problem when using grunt-rev together with grunt-contrib-compress and gzip compression.

I configured my compress task to change file extensions of gzip compressed files to .css.gz using the ext option:

{
  expand: true,
  cwd: 'dist/htdocs/',
  dest: 'dist/htdocs/',
  src: ['**/*.css'],
  ext: '.css.gz' 
}

Everything fine - almost. Except that
my 59c28e95.test.css was renamed to 59c28e95.css.gz
my 17575a8d.vendor.css was renamed to 17575a8d.css.gz
etc.

I know it's probably a "bug" in compress or in the grunt (or even node) file reader/writer/glob but nevertheless I added an optional separator option so you can at least workaround this problem by having your files renamed to 59c28e95-test.css instead of 59c28e95.test.css for example (dash instead of dot).

Merge it if you like :)

PS: I know I could have just flipped the execution order of the compress and the rev task but it seemed like a more "reliable" way doing it that way ;)

[chaizhenhua]

@manuelbieh I had just try this feature. when i set separator option to '-' or '_', grunt can not update index.html to reference revved .css, .js file.