[brain] adding activeadmin. integrating it with User model using 'rails generate active_admin:resource User'
[brain] saving thoughts
[brain] saving thoughs
[brain] adding model Tag.
[brain] adding one-to-many relationship (has_many/belongs_to) for user->thought and user->tag
[brain] added TagThoughtAssociation
[brain] made has_many :tag/thought to :tags/thoughts
[brain] added index to tag.user_id and thought.user_id
[brain] adding presence=>true in User,Thought,Tag,TagThoughtAssociation for all foreign keys
[brain] changing validates_presence_of to validates presence
[brain] fix validate not nill constraint
Merge branch 'active_admin'
[brain] merging active_admin
[brain] adding thoughts and tags to active_admin
[brain] adding dependent :destroy for destroying associated objects for users, tags, thoughts.
[brain] adding unique index on Tags for [user, label]
[brain] unique index to tta on [tag,thought]
[brain] more docs and todo