switch over to NodeRenderer-based tree showing
NodeRenderer for the AST
NodeRenderer for AnnotatedTree showing the annotation as (multiple) separate nodes
comment on need for well-typed instance for tuples
implement and use a generic NodeRenderer instance for left-tuples of three
NodeRenderer for Attr
redundant NodeRenderer for Node
expand annotation sub-trees
major cleanup

removed redundant Show instances
renamed to RenderTree, etc.
fixed tuple instance using implicit priority trick
RenderTree.apply
switch to explicit implicit parameters everywhere
use implicit def/val consistently
Merge pull request #79 from mossprescott/prettify

Everything has a NodeRenderer now