Add tests for `Board.find_by_path`
Use `<<` for appending to string or array
Rename `arr` to `dirs`
Update documentation
Update gems
Reorder badges
Add instruction for MySQL
Merge pull request #134 from yous/test-find-by-path

Add tests for `Board.find_by_path`
Merge pull request #135 from yous/clean-up

Clean up