Added customfilename option

[bolora]

This is an option to add a custom file name in the options and replace the hard-coded '-blessed'

When used with grunt-bless:

bless: {
  css: {
    options: {
      'customfilename':'-whatever'
    },
    files: {
      'my-file-ie.css': 'my-file-input.css'
    }
  }
}

would produce:

my-file-ie.css my-file-ie-whatever1.css my-file-ie-whatever2.css

instead of:

my-file-ie.css my-file-ie-blessed1.css my-file-ie-blessed2.css

I did not add this to command line options

[paulyoung]

Thanks @bolora. I've been thinking about this a little bit myself.

I'm going to leave this open for now but might bring it over to the v4 branch in the near future. I'm hesitant to make changes to v3 due to lack of tests.

[bolora]

Awesome, let me know when you release v4

[paulyoung]

Closing, as this is now being tracked in #56.