Fix recursive dependency and large dist files

[SBoudrias]

1. Don't rely on self in the dependency (as you might guess, this creates quite the recursive dependency)
2. Remove tests/dev files from the package published to npm (.npmignore)
3. Delete coverage build artifact (I assume they were committed by mistake)

[dielduarte]

@SBoudrias WOW! It's a great PR for the project to work better now. Thanks for your time, let me know if you have any more suggestions.

[SBoudrias]

My pleasure :)