Add Support for old style classes

* resolves #8
* Only code change is in target.py, everything else is test updates.
* I updated (object|partial)_double_test to run each test with both old
  and new style classes.  These were the only tests with 'real failures'
* We can paramatarize everytest if we decide it is a good idea.
remove uneeded noqa
Merge pull request #13 from uber/tws-old-style-classes

Add Support for old style classes
Update test runner integration docs.
Update usage docs for new syntax and removal of "Double" class.
List Uber as copyright holder in the docs.
Add API documentation for user-facing public interfaces. Refs #10.
Add Travis CI build configuration.
Use rst for README and clean up package description.
Include doubles.targets in packages list.
Update file name of README inside setup.py.
Add docstrings to all remaining methods and classes. Closes #10.
Add contribution guidelines.
Add call count specific expectations.

* Add expect(Foo).method_name.never()
* Add expect(Foo).method_name.once()
* Update is_satisfied() to check call counts, will raise expectation
  error if the call count does not match the expected value.
Refactor how we handle call_count limits

* Raise right away
* Move to allowance so you can limit the number of times an allowance is
  called
* Add new allowance tests
Fix merge errors
Update call_count syntax

* Duplicate rspecs exactly(n).times