[MAYBE MERGE] 768 leave project option

- Since functionality implemented uses the share endpoint to for users to remove themselves when leaving a project, users with ```readonly``` and ```dataentry``` roles cannot remove themselves from a project. The resolution would be to add permissions for users with these roles to be able to remove themselves from the project ```share``` endpoint or create a project  ```leave``` endpoint.

- This test (https://github.com/onaio/zebra/blob/768_leave_project_option/test/cljs/ona/home_test.cljs#L36) in home_test.cljs is causing ```lein cljsbuild test``` to hang due to the error:
```Don't know how to make node from: #<[object DOMWindow].``` This needs to be resolved.

pretty sure this is about not having the DOM mocked