findClosest does not change order of provided array
Fix: animation bug for tiles with no future times

Was throwing an error when attempting to go to a
future time, when the layer had no future times available.

This fix also improves transisions, when tiles are are not loaded.
When transitioning to a not-yet-loaded tile layer, the animation
will instead show the closest available layer in the same tense.
This prevents the empty animations you may see when running through
an animation loop for the first time.
Refactor spec helper method

for TileAnimation. To make spec bootstrapping
a little bit simpler
Update version to 0.7.10