Simplify Makefile
Use strict and fixup quotes
Some code style cleanup
Initial reset for v2.0
Initial work on digraphs

Basic node operations added.
Initial pass at edge handling for digraph
Add general edge query to digraph
Add initial benchmarks
Only run travis-ci on node 0.10
Add some graph query functions
Optimize updates to an edge's label
Use lodash
Initial implementation for copy
Change representation of edges to simplify code
Exploring different internal representations

This approach yields a significant (100x) speedup for setDeleteEdges at
1K nodes, 200K edges, without a significant impact on any other measured
function.
Add outEdges query
Some benchmark refactoring and more benchmark tests
Additional benchmarks
Use 'dot' reporter for mocha
Yet more benchmarks