Issue 194; rxFeedback 

This PR creates a new component that is added to rxApp, allowing users to send feedback from any app and from any page. 

![image](https://cloud.githubusercontent.com/assets/706039/3135410/ac46b6ec-e832-11e3-9732-99e547c70a4f.png)

![image](https://cloud.githubusercontent.com/assets/706039/3135414/b55196da-e832-11e3-855b-51d7805268af.png)


TODO (in a later PR):
- Add jsdocs for functions
- Include usage information in README file
- Custom fallback for encore-ui demo page (should take you to the issues page with details filled out)
- Move rxScreenshotSvc into a separate component