Add RSpec 3 Test Double support.

I made this change so that the RSpec Test Double support would be compatible
with RSpec 3 as well. This is necessary because they changed the public facing
API in RSpec 3.
Change :: to . for method calls.

I did this because it is clearer in terms of identifying them as method calls
and not classes.
Merge pull request #689 from cyphactor/add_rspec_3_test_double_support

Add RSpec 3 Test Double support.