use HTTPS for homepage URL in gemspec
add MIT license metadata to gemspec
add Gemfile

This allows us to use bundler with literati.
make tests work with bundler

With this commit, the test suite runs under bundler:

  bundle install
  bundle exec rake test
remove contest gem dependency

This gem is deprecated upstream. Remove it, and replace it with ordinary
Minitest::Spec functions.
Merge pull request #12 from ktdreyer/bundler-and-minitest

add bundler and switch to minitest
Merge pull request #11 from ktdreyer/gemspec

update gemspec metadata