Use ruby 1.8 syntax for hashes
Update README.rdoc

fix travis-ci image url
Merge pull request #540 from lucianosousa/patch-2

Update README.rdoc
Merge pull request #538 from AbleTech/feature/fix_ruby_1.8.7_failures

Use ruby 1.8 syntax for hashes
Merge branch 'master' of github.com:mongomapper/mongomapper into feature/faulty_sort_method