preserve alias case while lowercasing taxonomy

* Changed MakePath so that it preserves original case. 
* Added a MakePathToLower that lowercases the generated path. 
* Modified kp in taxonomy.go to call the new MakePathToLower instead of the original MakePath.
* Added and modified tests for MakePath and MakePathToLower.

A search on `MakePath` in the repo did not return any other cases of it being used. 

The affect on tags is unknown.