upgrade JDK from 1.6 to 1.7
add tests case to improve coverage.
close #11: add `reports` attribute to findbugs.xml.
add new detector which uses Guava's @VisibleForTesting.
close #22: detect FindBugs warning which has no justification.
Merge pull request #20 from eller86/improve-coverage

Improve coverage
Merge pull request #21 from eller86/11-add-reported-attribute

add `reports` attribute to findbugs.xml.
improve error handling: notice which class has problem clearly
Merge remote-tracking branch 'worksap/master' into visible-for-testing

Conflicts:
	README.md
Merge pull request #23 from KengoTODA/visible-for-testing

Introducing 2 new detectors which checks annotation