Initial bare-bones implementation of decorator and custom errors.

First 'master' release of the package. Should be mostly backwards-compatible with the [0.1.x version](https://pypi.python.org/pypi/Flask-Nicely) currently on PyPI, but cleans up the internals and adds additional functionality in the form of custom error payloads inspired by the [Flask API Error](http://flask.pocoo.org/docs/patterns/apierrors/) pattern.

Release needs:
- [x] Refactored internals to use httplib for generic error messages
- [x] Tox testing for Python 3.x compatibility and multi-version Travis CI testing
- [x] Improved documentation:
    - Why should anyone use Flask-Nicely?
    - How do I run multi-version tests locally?
    - What Python versions are supported?
    - General formatting
- [x] Changelog
- [x] Updated examples to show that status codes are now returned as integers.

Should close #1 and #2.