Initial release

This is the initial release of Guppy, which should have all the described functions at least minimally functional and documented.

Supports:

• Entry of basic mathematical expressions suitable for courses up to calculus
• Keyboard navigation and selection
• Cut, copy, paste, undo, redo
• Embedding editor into a page
• Javascript functions to extract state in XML, ASCII, and LaTeX form

Missing:

• Tests
• Documentation of internal format
• Documentation for how to add new symbols
• Some prettification of rendering