Force no_timeout in mongoid adapter

[prathe]

I can't index without no_timeout. Indexation of my model takes 5 hours.

[karmi]

Makes sense, thanks, merged!

[miguelff]

Noticed in #366 That this change has made the build unstable (Re: travis).

 ERROR (0:00:00.022) test_: Adapter Mongoid module: Importing should implement the __find_in_batches method.
          undefined method `no_timeout' for []:Array
        @ lib/elasticsearch/model/adapters/mongoid.rb:69:in `__find_in_batches'
          test/unit/adapter_mongoid_test.rb:82:in `block (3 levels) in <class:AdapterMongoidTest>'
          /Users/miguel/.rvm/gems/ruby-2.1.5/gems/shoulda-context-1.2.1/lib/shoulda/context/context.rb:413:in `instance_exec'

I'll fix it in another PR