Feature/cleanup path templates

Couple of things here:

1. Made some adjustments to the parsing implementation. While the regular expression is simpler it cannot detect all the possible syntax errors you might encounter (i.e. `@“}{“` or `@“{variable}_{variable2}”`). I am pretty confident the `NSScanner` could can be polished further.
1. Cleaned up API a bit by removing the initializer.
1. Blew out the docs.

Let me know what you think @Kurry and merge to master if you are happy.