v0.8.70

Commit	Message/Description
93c96f4	v0.8.70
a3864cc	Led.Matrix: Adds built-in characters for 00-99
bb5bd68	Board: Document that serialport.list() never errors. Fixes #768
17d5342	Update stepper-four_wire.js
2a4e0dc	Repl: non-essential nit picking.
4b9a236	Board: typeof foo === "undefined" is sufficient.
070d39b	Remove test/distance.js (no longer necessary, migrated to Proximity)
079f8b7	Board: comment cleanup
8538f57	Proximity: additional confirmed Ultrasonic pulse components