Fixes #15: Add a contributing file.
Fixes #15: Add a contributing file.

eXolnet/redmine-code-audit,eXolnet/redmine-code-audit,TomzxForks/redmine-code-audit,TomzxForks/redmine-code-audit,TomzxForks/redmine-code-audit,eXolnet/redmine-code-audit,eXolnet/redmine-code-audit