Issue 8 basic validation

Added basic validation for form and JSON submission. Used the [voluptuous](https://github.com/alecthomas/voluptuous) library for this, which offers a pretty 
nice API for specifying the structure of Python data structures.

Additionally, tidied up views.py and the respective templates to avoid using a bizarre _additional_info function.

fixes #8 
Good call—turns out those answers are missing at least a couple cases, too… I believe my (soon to be pushed) solution handles all cases. That belief is likely to be shattered, like so many others in the past have been.