Fixes #238. Fix markdown directive, rejig user API, remove old ID references. 

Add user serializer to not give out user email address over unprotected API show. Fixes #238 

# What's new
* Added user serializer to not give out email address over unauthorized API access
* Add show to skip_before_action so that the user is fetched from the API when non-logged in users view a guide.
* Fix markdown directory reference in Angular (I think?)
* Removed references to GUIDE_ID, AUTH_TOKEN, and USER_ID.
* Simplified password field

# What's next?
* Is there a way to specify two different API serializers for the same endpoint? Probably.
* Add rating to guides.