Add active record migration files

Create tables:
- users
- songs
- votes
- comments
- reviews
Delete reviews table migration file

Comments is now a self-referential association.

Change comment functionality of application. A 'review' or primary user reply of a song is now known as a comment. A comment can have many reply comments. There is no longer a distinction between a longer reply aka 'review' and a shorter reply aka 'comment'. When a user comments she can choose how she'd like to format the comment and the primary purpose of her comment. All comments on a song will be shown together. Comment replies will be nested.
Add Users database migration

User has:
- name
- email
- password hash
- bio
- url of bio photo
Create songs database migration

Song has:
- title
- artist
- album
- user_id foreign key (one to many relationship)

Removed planned support for user submitted album artwork capability. Artwork will not be stored locally and the Song class will not know it's album artwork.
Add comments database migration

Comments has:
- content
- song_id foreign key (one to many relationship)
- user_id foreign key (one to many relationship)
- parent_id foreign key (self referential association comment/reply to comment)
Create votes database migration

Votes has:
- votes_value (-1 value for downvote, +1 value to upvote)
- polymorphic association (vote can belong to a song or a comment)
Create active record models
Add active record model associations
Fix syntax error create_votes and create_users
Merge database creation branch

Merge branch 'master' of https://github.com/zkarst/diggit