Align the AST with the syntax of GADT declarations. Fixes #149.
Add test case for #149.
Document GadtDecl
Support default associated types. Fixes #153.
Add test case for #153.
Adjust precedence for prettyprinting infixapp. Fixes #152.
Add support for InstanceSigs. Fixes #89. Fixes #154.
Add test case for #89.
Document instance and declaration heads and rules
Avoid conflating lists of constructors and qualified quasi quotes. Fixes #155.
Add test case for #155.
Changed representation of negated patterns

See #13 and #106 for discussion.

Closes #13.
Added test for pretty/exact printing new negated literal patterns
Added tests for parentheses insertion by the pretty-printer.