Second attempt at fixing the secure access problem.
Changing the auto-install method.
Enabling a linter.
Merge pull request #448 from mithro/sauce-pull-fix-2

Second attempt at fixing the secure access problem.
Teach Web Animations about step-start, step-middle, step-end shorthands.
returnValue is part of BeforeUnloadEvent
Merge pull request #451 from arv/remove-return-value

returnValue should not be part of TimingEvent
Merge pull request #449 from shans/step-shorthands

Teach Web Animations about step-start, step-middle, step-end shorthands.
Merge remote-tracking branch 'up/master' into enable-linter
Lint fixes.
Merge pull request #447 from mithro/lint-fixes

Enabling a linter for web-animations.js and fixing the lint issues it found
Fix isCustomAnimationEffect()

We should allow objects with a sample() method to be used as custom effects,
even if that sample() method is on the prototype.
Make use of Timing._invalidateTimingFunction() to avoid code duplication
Rename SplineTimingFunction to CubicBezierTimingFunction
Modify PacedTimingFunction to operate over a range

This will be required to implement chained timing functions.
Merge pull request #452 from steveblock/chainedTimingFunctionsPrecursor

Preparatory work for chained timing functions
Add LinearTimingFunction

Currently we implement a linear timing function by setting
Timing._timingFunction to null and special-casing this in TimedItem. Adding a
separate type will simplify the logic in TimedItem and will greatly simplify
chained timing functions.
Implement chained timing functions

These are specified through the following attributes on Timing ...
- easing: A space-separated list of timing functions
- easingPoints: An array of the end points of the input/output ranges over
  which the timing functions apply. The following keywords are also
  allowed ...
  - distribute: Distribute timing functions evenly in time.
  - align: If the TimedItem with which this Timing object is associated is an
    Animation with a keyframe or path effect, align timing functions with
    keyframes.

See http://dev.w3.org/fxtf/web-animations/#timing-function-chains for details.

Note that alignment with a path effect is not yet implemented.
Use a single linear timing function if the specified string is invalid
Merge pull request #445 from steveblock/chainedTimingFunctions

Implement chained timing functions