Added options object that allows the user turn off the output file hash,...

... and also include a version string in the filename.

Tests pass.

  ✓ should rev files
  ✓ should not rev files if hash is false
  ✓ should rev and version if version set
  ✓ should not rev but add version if version set and hash is false
  ✓ should build a rev manifest file
  ✓ should allow naming the manifest file
  ✓ should append to an existing rev manifest file
  ✓ should respect directories
  ✓ should store the hashes for later

  9 passing (17ms)
Similar to above comment, allows one to use separate configurations for different environments, and better customize the rev in each. For instance, one could version stamp files for better debugging in QA environments, but not necessarily in production.

Also allows the developer to use a version string to cache bust the filename if they chose, instead of an unreadable hash.

I'm just providing more options, which are obviously secondary to the primary functionality of the plugin.