Fix subgraphs not traveling up predecessors on digraphs

Closes #89.
Don't hardcode the libraries to snap.berkeley.edu

Fixes #88.
Add local graph file import

Closes #86.
Add defaults for set label dialogs

Closes #96.
Fix edge attribute serialization
Add default for node/edge color dialog
Add defaults for node radius and edge width dialogs
Fix "add edge" dialog not giving focus to second part

Closes #97.
Add submenu for export to file
Use a proper CSV parser to handle edge cases in format
Add adjacency matrix CSV export
Comment out some leftover console.log() calls
Merge pull request #99 from Muon/master

Subgraph fix, library menu fix, local graph import, dialog defaults, improved CSV parsing