Revert "Changelog for #466 and #468"

This reverts commit bcb16de02bb3a6cbf1797bfd3f7d56022203b854.
Add a new test file to hold the viewport tests, and a few new tests to it.
Add viewport.js to test.html so tests get run. Use built-in Point functions. Add a helper function to get a random number.
Added Gitter badge
Use propEqual to verify Point values, add a stub test for imageToWindowCoordinates
add test for windowToImageCoordinates
Merge remote-tracking branch 'origin/master' into viewport-tests
imageToViewerElementCoordinates and imageToWindowCoordinates
viewerElementToImageCoordinates
First stab at margins
Cleanup and docs for margins
Merge pull request #501 from gitter-badger/gitter-badge

Add a Gitter chat badge to README.md
More margins work
Fix a bad merge of changelog.txt
Merge remote-tracking branch 'origin/master' into viewport-tests
Take out multiplication to avoid precision errors because it doesn't; add viewportToImageRectangle test
Fixed issue with top/left margins; cleaned up naming
Force a zoom factor of 2 and make that a constant; find the viewer position in the window for imageToWindowCoordinates (still not sure where the 20 x 20 pixel padding is coming from
More constants, fewer magic numbers.
Merge branch 'collections' into margins

fixed Conflicts:
	test/demo/collections/main.js