Fix exception caused when default value is 0.

Cherry picked from:

https://github.com/digium/swagger-py/commit/0a87b3b3892db053c23712fb3ac5e3c13b41045b
Properly quote paths within HTTP URLs.

Cherry picked from:
https://github.com/digium/swagger-py/commit/f0d272872ef9948ed84bed06ec94c8036902ef1d
Merge pull request #54 from wting/fix_truthiness

Fix exception caused when default value is 0.
Merge pull request #55 from wting/quote_paths_in_urls

Properly quote paths within HTTP URLs.
Remove websocket support.

It's currently unused, and doesn't have good tests.
Merge pull request #59 from jnb/remove_websockets

Remove websocket support.
Relax validation rules just a little bit.

* Successfully validate dicts that have additional fields beyond those
  specified in the associated model.
* Store raw deserialized JSON in '_raw' attribute of objects.
* Ignore '_raw' attribute in object equality checks.
Merge pull request #61 from jnb/relaxed_validation

Relax validation rules just a little bit.
change format='date' objects to use datetime.date representation
Merge pull request #62 from mjbryant/mbryant-dates-are-dates

change format='date' objects to use datetime.date representation