Checkstyle Sonar plugin 3.6

[Roman Ivanov]

Short description of the version: 

Issue #81: upgrade to checkstyle 7.6
Issue #32: wercker badge was added to README.md
Issue #32: wercker to test installation
Issue #32: basic wercker build file is created
Issue #32: Dockerfile creation for plugin testing in CI
Issue #75: Options for WhitespaceAround too long, type is changed from s[...] to STRING
Issue #45: resolved many checkstyle violations
Issue #45: resolved multiple simple formatting violations
Issue #60: added custom header for project
Issue #71: fix Violation at sonarqube.com
Issue #68: Lessen dependency on Guava
Issue #49: Reduce rule violations

SQ versions compatibility: 5.6.4

JDK: 1.8

Change log URL: https://github.com/checkstyle/sonar-checkstyle/releases/tag/3.6

Download URL: https://github.com/checkstyle/sonar-checkstyle/releases/download/3.6/checkstyle-sonar-plugin-3.6.jar