Fix uppercase bug (issue 63)

Quick fix to keep the uppercase letters in the path for the generation of Kotlin classes.
It was only tested on my (linux) computer.

See https://github.com/dukeboard/kevoree-modeling-framework/issues/63 for further details about the bug.
That may be you issue. 
However, you have to keep the lowercasing on  the package.
Just apply the lowercase before the concatenation to the existing path:
```fqn(pack).toLowerCase().replace(".", "/") + "/";``` for instance