Added feature to remove extra slash from source path to prevent doubling...

... of slash character in report output.

I chose to do a simple chomp rather than removing all ```/``` with a regex because the chomp is clearer to read and understand and while people may put an extra slash at the end of the path likewise: ```reek lib/``` if they put ```reek lib///``` (which is still valid) they probably have made a typing error.

Resolves issue #176.