Noticeable improvements

Changelog:

• configuration option to include/exclude test files - #16
• configuration option to set maximum number of comments - #16
• support for configurable URL path - #17
• better example configuration - #20
• Stash won't add same comment on a line twice - #19 , #22
• Stash configuration option to comment only on changed lines - #13
• Gerrit won't add deleted files to review - #1
• code and test refactoring