Float to Integer Fix for 'px' values in Navigator

Also fixes unit tests on Firefox (#332)
Fix for IE 11 Browser Detection

Proposed temporary fix until we don't need browser  sniffing anymore.
Add Double-Click/Tap Gesture to MouseTracker (#300)

Fix for enhancement #300
Added double-click/tap gesture detection to MouseTracker.with
corresponding dblClickHandler event callback.
Added unit test for double-click detection.
Added Viewer dblClickHandler handling to optionally zoom on
double-click.
Update changelog.txt

Updated changelog.

Misc documentation fixes.
Merged upstream changes, fixed conflicts
Merge remote-tracking branch 'origin/master' into Firefox-Unit-Tests
Merge remote-tracking branch 'origin/master' into IE-Browser-Detection
Merge pull request #384 from msalsbery/Firefox-Unit-Tests

Float to Integer Fix for 'px' String Values in Navigator
Merge pull request #385 from msalsbery/IE-Browser-Detection

Fix for IE 11 Browser Detection
Merge pull request #392 from msalsbery/Double-Tap

Add Double-Click/Tap Gesture to MouseTracker (#300)