Tkinter GUI

Here is an rather rough, alpha-quality Tkinter GUI, which might be of use. I've added some extra features, first is that you can plot multiple variables, one filled and one contoured. Of course you can have also the same variable filled and contoured. Another change is that the text at the bottom of the graph below timestamp can be customized inside the GUI. Last, rendering winds is now optional. This way CONUS images can be created without much clutter. Let's see if I got this procedure right given I am rather new to GitHub. Example of the output in the new system:
![figure_1](https://f.cloud.github.com/assets/4496818/1276324/5918d022-2e5b-11e3-869b-6eb77af74cb3.png)