Rationalize dependencies for use in browser

- Grab dependencies from global if available, else use `require`
- Add bower.json
- Explicitly show dependencies in README
Expose createUserGroup method

Will be used by Blip on account creation and patient profile creation
(to create "patients" group and "team" group, respectively).
Add back superagent as dependency injection

Create `tidepool.js` that wraps contructor passing along necessary
dependencies, for app developers to use.
switch to use tidepool.js and pass host option
also need to check the dependancy is not undefined on the window object
Merge pull request #1 from tidepool-org/blip-integration

Blip integration