use general file resolution for test files as well

the special-purpose file resolution method for test/spec files was failing
with namespaced test files (ex. User model attributes would annotate both
test/unit/user_test.rb as well as test/unit/foo/user_test.rb, instead of
only the former)
switch deprecated "mock" for "double" in annotate specs

changing to get rid of deprecation warnings
Merge pull request #166 from jonoterc/namespacefix

fix overwriting of namespaced model test annotations with non-namespaced model annotations