CanonicalPath v0.3.0.0

Recently there was the third major release of CanonicalPath library introducing some good stuff, but unfortunately breaking API (just a tiny little bit).

The new version is available on Github, Hackage and Stackage.

• Remove UnsafePath data type. It was a synonym to FilePath and was confusing me sometimes, so I decided to cut it off.
• Rename cpathToText to toText'.
• Remove pathToText and textToPath.
• Export toText and fromText from Filesystem.Path.CurrentOS.
• Export fromPrelude and toPrelude functions.
• Improve performance (path canonicalization now is performed 1.6x faster than before). Now that I have tests and criterion, I can measure performance.
• Improve canonicalPath error messages. Most important - now it respects errors from System.Directory.canonicalizePath.
• Add tests.
• Add Travis support.
• Update documentation.

As always - suggestions and pull requests are welcome!