Add organizations to the volunteer db

**DO NOT MERGE**  This needs styling and some minor tweaks to when certain links are shown to organization admins.

### What is the problem / feature ?

There were no organizations!

### What still needs to be done.

Style the following pages
- `/organizations/` - list of all organizations.
- `/organizations/1/` - detail view of an organization
- `/organizations/1/edit/` - edit one of the organizations you are an admin for
- `/organizations/1/manage-members/` - manage the memberships to an organization you are an admin for.
- `/organizations/1/manage-requests/` - manage requests to join a closed organization.
- `/shifts/leaderboard/` - organization based leaderboard.
- `/accounts/my-organizations/` - manage your own membership organizations.

### How did it get fixed / implemented ?

Added a bunch of stuff for the following functionality.

- Creation of closed and open organization.
- Administration of organization members.
- Request system for joining organizations
- Leaderboard based on organization member volunteer hours.
- Management of your own organization memberships.

### How can someone test / see it ?

- See the new organizations top-nav menu item.
- Create an organization.
- Claim some shifts
- See the leaderboard

*Here is a cute baby animal picture for your troubles...*

![tumblr_m2hzvach0i1qi0jmeo1_1280](https://cloud.githubusercontent.com/assets/824194/2686383/c551f694-c1fc-11e3-841f-17b6ad7dc9a1.jpg)