Ability to create User split into own line, and remove ability to create Iterations for persisted users.
User can update and destroy Snippets, Comments and Votes that belong to them.
Add ability to create, update and destroy Iterations and Shares that belong to a Snippet owned by the user.
Fix syntax errors in ability file.
Edit link on snippets (new iteration path) only appears if user can update snippets.
Authorize Iteration create action.
Authorize Iteration new action.