Support to escape a directory for mapped version

[mokesmokes]

You can now do versionator.createMapped(staticFileMap, 'myEscapedDirectory');, where the escaped directory will not be reverse-mapped with the hash. This is mostly required to serve CSS files that use resources with relative paths. An example would be select2.css. So I can put select2.css and select2.png in directory /css/myEscapedDirectory/select2-3.4.1/ and use link(rel='stylesheet', href='/css/myEscapedDirectory/select2-3.4.1/select2.css), and maintain versioning elsewhere.
The implementation looks for the escaped string in req.url, so you can have multiple escaped directories in your file structure (e.g. in both css and javascript directories).

[serby]

Can you provide some tests for this feature.

[mokesmokes]

I don't think I'll have time to do this in the near future, but I can assure you I have been using this for a few months without a hitch. My production use case is exactly as specified above.