Closes #2614

![2614](https://cloud.githubusercontent.com/assets/319128/2747513/932f05ac-c770-11e3-86c0-b36fdc7ad6b9.gif)

- When no text is selected insert link markdown and move cursor to a into the [] portion.
- When text is selected insert link markdown and move selection to http:// text so proper link can be pasted right away.