tidying up

- Using Bundler [1] to manage installed gems for the project.

- RCov does not support Ruby 1.9.X. The RCov github page suggests using
SimpleCov [2] instead.

- There were also a couple or `require` statements in the Rakefile
that were causing problems (errors, etc) after new gem versions and the
like.

- Removed all trailing whitespace and extra blank lines.

- Including .travis.yml to run the tests using Travis-CI [3]
for Ruby 1.9.3 and 2.0.0.

- Added development dependencies, executables, and exclusions to the
gemspec.

[1] http://gembundler.com
[2] https://github.com/colszowka/simplecov
[3] http://travis-ci.org