Remove months_in_project from available people

Moving this feature to users view
issues #45
Add months_in_project to user

issues #45
Expose months_in_project to gon.users

issues #45
Add gon.months

issues #45
Add months_in_project select to users index view

issues #45
Filter months in backbone user model

issues #45
Selective the dropdown and filter users

issues #45
Styling

issues #45