Removed Gemfile.lock (was preventing the travis build from running) and tidied up .travis.yml
Removed old tag for Rational#div
Added tags for tests that completely stall mspec when run using MRI
Added continuation and fiber the libraries ignored by mspec in ruby 1.8 (based on the mspec config for jruby and rubinius)
Corrected the travis status image so it only shows master and not the most recently changed branch