Add state description to membership docs

Closes #371
Fix roundness typo

Closes #374
Convert to new Locations Format

Locations becomes an array of available media. Create and Update
methods accept an array of mime types. If a particular peice of media
has multiple representations they should be sent as a comma-seperated
string of mime types.

Examples:

two jpeg images

```
"locations": ["image/jpeg", "image/jpeg"]
```

A single video encoded multiple ways

```
"locations": ["video/webm,video/mp4"]
```

Closes #369 Closes #341
Merge pull request #380 from edpaget/fix-workflow-docs-typo

Fix roundness typo
Merge pull request #379 from edpaget/update-membership-docs

Add state description to membership docs
Merge pull request #376 from edpaget/subject-api

Convert to new Locations Format
Allow ids to be either strings or integers

Closes #372