added 'exclude by regex' option to exclude commits from commit regex and jira issue checks if part of commit message matches regex. #17

cleaned up README.md

'exclude merge commits' setting now only excludes commit from commit regex and jira issue checks. committer name and email checks are still applied if they are enabled.
initial checkstyle integration to fix indentation inconsistencies. source code has violations right now, but I want to make sure checkstyle is working in travis.ci before I fix them.
made indentation consistent. replaced tabs with 4 space indents
fixed checkstyle configuration
reverted travis.yml change