Output rp-array.json and rp-string.json

[TheJaredWilcurt]

The default classMap from red-perfume-css uses arrays of atomized classes, like so:

{
  ".cat": ["rp_3", "rp_5"],
  ".dog": ["rp_0", "rp_4", "rp_8"]
}

Because a class name can contain any character (as long as it is properly escaped), splitting a string back to an array has slightly more edge cases to it than joining an array to a string. So to avoid the edge cases, we will always store the classMap as an array. However, I suspect the majority of users will prefer having the JSON already in a joined string format. So perhaps the easiest option is to just output both during the JS task.

{
  ".cat": "rp_3 rp_5",
  ".dog": "rp_0 rp_4 rp_8"
}

Related to #12