Remove cookie from Frontend

closes #1437
closes #1472

- changed cookie to path:'/ghost'
- added conditional CSRF middleware
- added redirects for signup, signin, signout to /ghost/sign*/
Merge pull request #1570 from sebgie/issue#1437

Remove cookie from Frontend
Fix failing migration.reset for Postgres.

refs #1333
bumping to knex 0.5 and bookshelf 0.6.1