Handle Ruby syntax errors.

To make this process easier a new class was created: RubyLint::Runner. This
class acts as a easy to use layer around the various parts of ruby-lint so that
you can analyze code without having to do everything yourself.

Signed-off-by: Yorick Peterse <yorickpeterse@gmail.com>
Add JSON as a development dependency.

Signed-off-by: Yorick Peterse <yorickpeterse@gmail.com>