Front and Backend for Project Page

#### Front end

- Each project has its own page
- Can edit project name and description
- Can edit each of the project's openings
  - Name, description, pay type, pay amount, timeframe
  - Add and remove skills (with Chosen jQuery plugin)
  - Cancel or save changes
- Can add a new opening
- `Skill` resource in `resources.js`

#### Backend

- Support for creating/updating with skills in Opening
  - Also adds same support to User
- Support for admins creating, updating and deleting skills
- Made JSON API routes prefixed with `/api`