Make rubygems-bundler work properly.

As I have bundler and rubygems-bundler installed in my "base" ruby configuration
I don't need them to be installed for the application. This commit removes them
from the Gemfile.

See https://github.com/mpapis/rubygems-bundler for details of how it works.
Rename test Rake task

This calls the rake test task `test`, and makes it the default explicitly.
Add `rake rdoc` task

This generates documentation for all the classes, and adds a .gitignore
so that we don't stash the generated HTML files in git.