Add Report Bug Button within Light Table

This is a fix in response to issue #125. There has been a button added to the Light Table Welcome Screen that allows the user to click and report issues on GitHub. There is also a "Report an Issue" Help menu item that allows the user to do the same. 

![reportissue](https://f.cloud.github.com/assets/5749454/2203374/8b1f64a6-991c-11e3-99fe-74b336e1dcc2.png)