allow null target on Animation constructor
Remove use of JS functions that aren't supported in IE.
Work around lack of IE <template> support.
Merge pull request #233 from rjwright/IETests

Fix interpolation tests and runner to run on IE
Merge pull request #230 from samthor/play_null_target

allow null target on Animation constructor
Revert "check for NaN in calculateTransformedTime"
Merge pull request #234 from web-animations/revert-225-check-nan-timing

Revert "check for NaN in calculateTransformedTime"
Merge remote-tracking branch 'web-animations-next/master' into HEAD
Add build artifacts from 4dffbf496739089dc59d1a86ccd77be15c686da6