Download the JavaDoc and Sources without throwing exception if an artifact doesn't exist.
Merge pull request #55 from SuperJugy/ArtifactsFix

Download the JavaDoc and Sources without throwing exception. closes #54.
Released V1.6.1 to Maven Central
Prepare for next Iteration
Update to Gradle 2.1, Android plugin 0.13.0 and coveralls plugin 2.0.0