Change package name to remove references to foxopen.
This project has nothing to do with FOXopen other than that I use
FOXopen in my day job. Most of the work I do on the JIRAChangelogBuilder
project is done in my spare time.

This has the side-effect of not being able to reload cached versions as
these are simply serialised Java object using the old package name. To
mitigate this I have added a catch for ClassCastException that will
return null thus bypassing the cache and forcing a reload for this
version.
Tidy up.

Tidied up the tests with the following:
- All test files now get written to ./test_output rather than polluting
  the root of the project.
- Renamed credentials.properties to testing.properties as it contains
  more than just credentials. Also updated README.md to reflect this.

Removed build.xml left over from when ant was being used.

Renamed LICENCE.txt to LICENCE to be more standard.