Update Travis config to match supported versions
Update Travis config to match supported versions

1. Drop support for Ruby < 2.0 (https://www.ruby-lang.org/en/news/2014/01/10/ruby-1-9-3-will-end-on-2015/)
2. Drop support for Rails < 4 (http://rubyonrails.org/security)
3. Test against only stable versions of the 4.0.* and 4.1.* versions of
   Rails and master

muthhus/griddler,Inchdev/griddler,r38y/griddler,Inchdev/griddler,Inchdev/griddler,RubyDaily/griddler,firepoint/griddler,iainsmith/griddler,r38y/griddler,pipefy/griddler,r38y/griddler,thoughtbot/griddler,danavery/griddler,thoughtbot/griddler,muthhus/griddler,ValiMail/griddler,iainsmith/griddler,joeadcock/griddler,ValiMail/griddler,muthhus/griddler,wingrunr21/griddler,danavery/griddler,bradpauly/griddler,seanscal/griddler,thoughtbot/griddler,joeadcock/griddler,bradpauly/griddler,wingrunr21/griddler,danavery/griddler,wingrunr21/griddler,pipefy/griddler,joeadcock/griddler,firepoint/griddler,vahtel/griddler,seanscal/griddler,firepoint/griddler,vahtel/griddler,ValiMail/griddler,vahtel/griddler,pipefy/griddler,seanscal/griddler,RubyDaily/griddler,RubyDaily/griddler