User now has_many :notes
Added Table model
Added relationships for Project. Closes #2

habtm users
has many columns
has one table
Adds relationships to Column. Closes #5

habtm table
has many items through checkoff
has many checkoffs
belongs to project
Added relationships to Checkoff. Closes #6

belongs to column
belongs to item
Added relationships to Item. Closes #7.

has many checkoffs
has many columns through checkoff
has one table as child
belongs to table