Add .gitignore file
Include Bundler and Rake to package the .gem file
Engine - add plugin description
Importer - avoid hard-coding a reference to the Node class
Fix respond_to? behavior

Depending on the version of Ruby / Rails, respond_to? can be invoiked
with a string or a symbol. With this commit we normalize the argument
into a symbol before comparing with the list of implemented methods (a
symbol array).
Add Gemfile to repo