Add validation and association test.

Migration to add size column to group
Display user count in groups relative to max group size
Fix current member size against max membersize display
Add feature to upload images to tutorials. Display the image when user
creates the specific tutorial.

NEED to fix sort
Merge branch 'master' of github.com:jmoon90/studygroup into improve_group_function

Conflicts:
	app/models/membership.rb
	spec/features/user_joins_group_spec.rb
	spec/models/group_spec.rb
Fix Bug in group controller with size not being set. Added size to
post_params white list
Add sort method in group controller and routes for sort
Create sort button need to write test
Add test sort button in group index page.
Fix css of group views
Change success message when creating groups
Created an nullify dependent on User to post and comments.

Changed anti pattern with the filter_params in Group controller so that
it can scale in the future
added stuff
Change filter_groups methods in controller to the model. Refactor
sorting methods so that it uses sql query
Refactor code from Group index. Took out logic and moved it to the
model. Added counter_cache to make queury faster
Refactor group sort methods. Changed method names to reflect more
closely of what they do
Merge branch 'counter_membership' into improve_group_function

Conflicts:
	app/controllers/groups_controller.rb
	app/models/group.rb
Merge pull request #9 from jmoon90/improve_group_function

Improve group function