Add software design

based on CRC cards session with David S and Camille.
Generate PDF instead

and add Makefile
Add png design as well
Update README.md
Update png
Building acceptance test for parser

- acceptance test for basic coversheet
- parslet transform for building models
Remove imported smart_answer code
Remove question base (not used)
Refactoring and more work on parsing

Refactoring to change the model so that a Node is a general purpose
representation of all page types. It will aggregate front_matter,
markdown content sections and 'widgets' corresponding to either
questions, outcomes or start buttons.
Add DirectoryInput to abstract reading files from filesystem
Cover sheet parser, refactoring

introduce 'Elements' which are the parts of a node.

introduce 'Interpreter' which are the combination of a parser and a transform
Break up node parser into parslets for each element