Maintenance release.  Optimizes, refactors and cleans up core code.

Squashed commit of the following:

commit c153f7a466df7e3011604f6c01744312317ebf8d
Author: Jeremy Kahn <jeremyckahn@gmail.com>
Date:   Thu Mar 20 21:48:43 2014 -0500

    Builds 1.0.7.

commit 8021c954a8048c87432d6c5803d1faf70d072ddc
Author: Jeremy Kahn <jeremyckahn@gmail.com>
Date:   Thu Mar 20 21:36:53 2014 -0500

    Cleans up .getStart.

commit e6af24dac8ce3c67a4637634853f9ab7ee5dd3c3
Author: Jeremy Kahn <jeremyckahn@gmail.com>
Date:   Wed Mar 19 18:24:05 2014 -0600

    Makes annotation fixes and adds better null checking.

commit 376fcd6dc7d9c2707d5f89256ebeddb0168f5270
Author: Jeremy Kahn <jeremyckahn@gmail.com>
Date:   Wed Mar 19 18:10:39 2014 -0600

    Cleans up various Actor methods.

commit 861d2970038ef5c207ba192853739ca9288b28f2
Author: Jeremy Kahn <jeremyckahn@gmail.com>
Date:   Wed Mar 19 17:44:21 2014 -0600

    Refactors hasKeyframeAt.

commit 0b2bd54b4ffee6d3c86948fc14dc545e72610baa
Author: Jeremy Kahn <jeremyckahn@gmail.com>
Date:   Wed Mar 19 17:24:52 2014 -0600

    Removes some redundant logic in .keyframe and reuses Shifty helper function.

commit b0a681de5bb8ac161facf55c1f2b51772f7e09a4
Author: Jeremy Kahn <jeremyckahn@gmail.com>
Date:   Wed Mar 19 12:29:59 2014 -0600

    Adds a few comments.

commit d72822c83b9a8411162bcf99c38cf1a32993ec0c
Author: Jeremy Kahn <jeremyckahn@gmail.com>
Date:   Wed Mar 19 12:19:48 2014 -0600

    Optimizes and cleans up invalidatePropertyCache.

commit 5c099a8e5474ea448ea4d920a628706db7686281
Author: Jeremy Kahn <jeremyckahn@gmail.com>
Date:   Wed Mar 19 12:00:40 2014 -0600

    Variable renames and doc fixes.

commit 1025719c20add6ddd63105cc85363b00442b0a1f
Author: Jeremy Kahn <jeremyckahn@gmail.com>
Date:   Wed Mar 19 11:47:12 2014 -0600

    Refactors and cleans up getLatestPropeties.

commit 35a45b0d2073051cd5c6fd5802efdab0cfa019e9
Author: Jeremy Kahn <jeremyckahn@gmail.com>
Date:   Tue Mar 18 22:09:58 2014 -0600

    Minor refactoring.

commit b505e4f7c8b31310f4ac1e15d6160d5da63968f9
Author: Jeremy Kahn <jeremyckahn@gmail.com>
Date:   Tue Mar 18 21:52:41 2014 -0600

    Cleans up and optimizes some private actor functions.