see also:
- https://gist.github.com/gkzhong/3916852
- http://www.javaworld.com/article/2077945/open-source-tools/automated-code-reviews-with-checkstyle--part-1.html
TODO:
- add rule to disallow private access modifiers
- are implementation classes contained in proper package?
- is there license inserted in new classes header?
- if permissions are involved - is there Authorization test?
- is there unit test for interface methods?