Improved docs

- Fixed an outdated URL
- Rewrote "Separate Celery" section
- Changed literal blocks to bash code-blocks
- Changed wording when referring to the MediaGoblin WSGI application
No more of this find_packages nonsense.

Explicitly declare mediagoblin as the only package.  find_packages has
caused messes in the past :)

This commit sponsored by Pedro Ângelo.  Thanks!
basic_auth v0 plugin working
reset mediagoblin.ini
added login.html template hook and basic_auth login template
moved forgot pw views to basic_auth plugin
moved normalize_user_or_email_field to auth/tools.py from auth/forms.py
changed User model pw_hash field to nullable and added migrations
add a check for authentication plugin on startup and respond according to no_auth config option. allows instance to be run w/o authentication
moved bcrypt_check_password to basic_auth/tools from auth/lib
moved bcrypt_gen_password_hash to basic_auth/tools and added gen_password_hash function to auth/__init__
modified check_login function to return None instead of False to be able to have multiple plugins check_login
renamed basic_auth/tools to basic_auth/lib
renamed hook as to no conflict with existing hook names
modified test .ini files and changed tests to use basic_auth bcrypt
existing test all passing now
changed from sys.exit() to raise AuthError for handling no_auth=false in config and no auth plugin present
added tests for no_auth feature
made basic_auth a default plugin
log a previously logged in user when switched to no_auth mode