Merge pull request #10 from akoumjian/develop

Refactor common  backend functions
bumps django to 1.5.4
Makes Post class customizable using STARDATE_POST_MODEL
setting and the get_post_model() function.

Closes #9
adds initial .travis.yml
fix travis settings
fixes sorting on post keys and allows for the
addition of arbitrary fields on BasePost subclasses

changes render method to make a copy of the post
dictionary that is passed in, instead of modifying
the dictionary in place when the body is popped

closes #8
adds get_env_variable to example settings
missing import
updates to setup.py
update travis settings
updates travis settings
stop testing python3.3 for now
updates example settings

adds stardate.management.commands to setup script
updates requirements.txt
Merge branch 'develop' of github.com:blturner/django-stardate into develop
add experimental gist backend