Now works on android build tools for gradle v0.11+

android build tools update to v0.11 changed the DefaultAndroidSourceSet.getJava() return type, so android-cp wasn't able to generate correct file set for checkstyle, pmd and cpd.  This fix utilises different approach and generates the fileset itself and works both on elder and newer versions.
Merge pull request #2 from ktarasenko/fileset_fix

Now works on android build tools for gradle v0.11+