Import existing work on Russet.
Improve documentation and naming.
Doc-tests, oh my.
Generalise Tokeniser.

Tokeniser now takes parameters for quote characters, escape
characters, and the escape prefix.
Add QuickCheck as a dependency.
Add add_line and simple whitespace-only tokeniser.
Add a QuickCheck test for the whitespace tokeniser.
Implement shell-style escaping.

Needs some unit testing.