Revert "Allow to pass options to associations"

This reverts commit c8cfe94f299619382d2178344e99d6c6d0e02cb1.
Allow only to pass scope to associations

Closes #483
Move the default value to the options param
Force install Bundler 1.5.1 as a workaround of http://changelog.travis-ci.com/post/71633370723/mri-ruby-2-1-0-and-jruby-1-7-9-available