Don't add a newline at end of files (and minor improvements)

I like your gem :) With the following changes, we actually use it gladly.

- Use spaces, not tabs for indentation
- Removed a superfluous space in the encoding comment
- Use Array#unshift instead of insert(0,...)
- Don't append a newline at the end of the file
- Add lib to load-path for local testing outside of the gem