New Option to Minimize/Maximize Mini-Map

Added a `toggleDisplay` option that can toggle the mini map from displayed to minimized (and back).  Only a few lines of javascript, three css tags and a small image file were needed to do this.

You can preview this using the example/example_toggleDisplay.html

![maximized](https://f.cloud.github.com/assets/795979/72351/69a2d106-600f-11e2-8012-b959e78a9db5.png)
![minimized](https://f.cloud.github.com/assets/795979/72352/69a10a60-600f-11e2-81b8-d7d75d4ead76.png)