Initial code for DotGraph / DotDigraph
Dot graph values must be objects only
First pass at support for defaults
Remove defaults functionality

Given that DOT only assigns defaults as they appear in the source file
we punt on trying to bake in any special behavior for defaults and
instead leave it to the parsing phase.
Simplify the writer code
Always remove reparented object from original parent
Support parsing / writing with Dot(Dig|G)raph

Fixes #4
Fixes #5
Ensure that return value from SuperConstructor is returned
More tests + don't add id attrs to nodes and edges
Move describe test block to DotDigraph-test and DotGraph-test
Only allow objects as values for Dot(Dig|G)raph
Add functions to conver from (Dig|G)raph to Dot(Dig|G)raph
Only quote ids when necessay
Add documentation for new DOT graphs
Prep v0.2.0 release