Update docs
Fix implementation
Merge with latest master
Tweaks
Tweak resource docs
add tests for OAuth authentication
add django-oauth-plus & oauth2 to installed apps in runtests settings.py
add OAuthAuthentication class
add django-oauth-plus & oauth2 to .travis.yml
add django-oauth-plus & oauth2 to optionals.txt
add OAuthAuthentication documentation stub
Add better date / datetime validation (pull 2)

addition to #631 with update to master + timefield support
Move oauth2 and django-oauth-plus imports to compat and fix some minor issues

- alias oauth2 as oauth
- remove rouge print
- remove docstring markups
- OAuthAuthentication.authenticate() now returns (user, token) two-tuple on success
- don't set request.user because it's already set
OAuth tests now are skipped unless django-oauth-plus and oauth2 are installed.
runtest.settings fixed if django-oauth-plus or oauth2 are not installed

oauth_provider can be added to INSTALLED_APPS only if these packages are installed
Fix for python 3 support - thanks @Linovia
Fix for python 3 support
oauth2 & django-oauth-plus installed only on 2.x
import compat version of unittest
rfc5849 link with anchor