Require Ruby version: >= 1.9.3
Fix dependency: active_support -> activesupport.
Remove ruby-1.9.2 from .travis.yml / #27
Update .travis.yml

ruby version for rvm:
2.1.0 -> 2.1.*
2.0.0 -> 2.0.*
1.9.3 -> 1.9.*
Bump version into 0.2.1
Merge branch 'hotfix/0.2.1'