- removed pmd library: now it is loaded from maven repo
- added pmd-java library into build.gradle so java rules are taken from repo not local custom jar
- upgraded Findbugs, Checkstyle and PMD, resolved problem with dependencies
- minor changes required by new PMD API
- better support in case when findbugs throws exception when there is no file for analyzing
Code review https://github.com/TouK/sputnik/pull/44
Merge branch 'master' into libs-upgrade-and-cleanup

Conflicts:
	src/main/java/pl/touk/sputnik/processor/pmd/PmdProcessor.java
comment fix
Merge pull request #44 from damianszczepanik/libs-upgrade-and-cleanup

Upgraded Findbugs, Checkstyle and PMD