Fix loadFromJSON 404s breaking fabric (Pattern)

Prevent image 404s in patterns from loadFromJSON from breaking
everything trying to get attributes of a source which is null, while
passing it upwards to allow dealing with images which failed to load
outside of Fabric.JS
Fix loadFromJSON 404s breaking fabric (Image)

Prevent image 404s in Images from loadFromJSON from breaking everything
trying to get attributes of a source which is null, while passing it
upwards to allow dealing with images which failed to load outside of
Fabric.JS Issue #1079
formatting for fixes
add spaces before {
Enable coverage
Build distribution
Add istanbul as dev dependency
2013 -> 2014
Update qunit
Fix event listeners for multi-input devices
Fix multiplier<1 export
added "_this" reference for setTimeout
Moves the resetting of _currentTransform.target inside `if (activeGroup)`

This solves a problem that occurred if you were transforming (moving, scaling, rotating) a single object
when toJSON()/toObject() was run.