Fix obsoleted rspec stub syntax.

The following syntax is invalid now:

    x.stub method, return_value

It should be change to

    x.stub method => return_value

or

    x.stub(method).and_return(return_value)
Merge pull request #428 from doitian/rails4-fix-obsolete-rspec-stub-syntax

[Rails4] Fix obsoleted rspec stub syntax.