Rspec specific changes

modified:   Rakefile
* Added the default gem tasks. Changed the test task to run the rspec
command.

	renamed:    test/rspec_test_upton.rb -> spec/upton_spec.rb
* The file naming convention is filename_spec.rb. Modified the files as
  per that.

	modified:   upton.gemspec
* Added rspec as a development dependency in the gemspec.