Move to circle 2.0

Move to circle 2.0

adds support for apex classes#26 (#29)Currently, Salesforce developers cannot use CodeClimate despite CodeClimate having PMD as a plugin. This is because the PMD plugin filters out all files that are not Java (.java). This patch allows for the Apex class extension to be processed as well (.cls).Related to#26

Merge pull request#28 from codeclimate/sl/update-pmdUpgrade codeclimate-pmd

Fix readup (#25)* Related tohttps://github.com/codeclimate/app/issues/5817* Remove bogus markdown - intended for PMD internal use only (#25)

Upgrade PMD to version 6.0.1 (#23)* Upgrade PMD to version 6* Adjust regression suite as the new version has different output values* Use new rules xml instead of group name, as they became incompatible* Speedup analysis with builtin cache* Redirect warnings to stderr* Hardcode ruleset as runtime directory changes

Adjust analysis config (#24)

Use community submitted engine to check groovy code (#22)

Replace default xml rules with rule names (#20)

Allow rules string as a configuration alternative (#19)