Removed mousenter/mouseleave DOM Event Handling

Fixes #394

mouseenter/mouseleave are not implemented in Webkit very well, so
reverted to mouseover/mouseout.
Merge pull request #395 from msalsbery/chrome-mouse

Removed mousenter/mouseleave DOM Event Handling
Changelog for #395
Removed mousenter/mouseleave DOM Event Handling from Unit Tests
Merge remote-tracking branch 'origin/master' into chrome-mouse
Improved Viewer Options Support in Gesture Handling

Apply constrainDuringPan option in flick and drag gesture handling.
Apply panHorizontal and panVertical options in flick and pinch gesture
handling.
Merge pull request #398 from msalsbery/chrome-mouse

Removed mousenter/mouseleave DOM Event Handling from Unit Tests
Merge pull request #399 from msalsbery/constrain-during-pan

Improved Viewer Options Support in Gesture Handling
Releasing 1.1.1
In progress 1.1.2
Added ImageLoader; loads batches of images using async queue pattern
Merge pull request #402 from rdlester/master

Added ImageLoader; loads batches of images using async queue pattern
Fix for IIPServer style urls when using DZI.
Merge pull request #413 from esmondb/master

Fix for IIPServer style urls when using DZI.
Changelog for #413
Updated to latest npm packages