add debug console to webapp

![screen shot 2014-11-24 at 12 36 40 pm](https://cloud.githubusercontent.com/assets/5429146/5172651/9bed47ae-73d6-11e4-98a2-873017f7e0b5.png)

* Added a debug console to webapp
* you can now inspect variables, call functions, and evaluate javascript in the context of your running program
This looks like it will not preserve state between subsequent commands. What about retaining the evalInterpreter state between commands and maybe only resetting it when the program advances? e.g. so you can do things like:
var x = 5;
x + 3
arguably these aren't useful for debugging, but they are useful for learning the language.