`System` class error in mass_spring_damper
Fixed System error
Modified direction in svg from x to y
Refined init conditions, constants for simulations,
mass spring damper working
reverted svg from "y" to "x"
Modified default camera
Fixed scene.js, cleared notebook output
using init_vprinting as per moorepants comment
Touch up comments.
Merge pull request #93 from pydy/mass_spring_damper

Updating mass_spring_damper example