Fix autosupport loading issue (See rails issue 14664), and add test for ruby 2.1.1

ActiveSupport might fail to load at random, and needs to be loaded differently. See https://github.com/rails/rails/issues/14664

Rails edge docs have been updated and specify to require Active Support core extensions like this: ( http://edgeguides.rubyonrails.org/active_support_core_extensions.html)

```ruby
require 'active_support'
require 'active_support/core_ext'
```

Please merge this and release 0.13.1, as using 0.13.0 can trigger this load error on random.

It occurs more often on ruby 2.1.1 than on 1.9.3 and 2.0.0, so I added 2.1.1 into the travis test matrix.