Pause and play children of a group

Trying to sort out setting start time

fixes after rebase. Time for another one!

Setting startTime on group players is working

Absolute hack job but setting current time on paused and playing groups seems to work.
Need to fix finished() for group players, among other things.
Need to compare against master to make sure I haven't removed anything important.

Cleaned up code. Setting startTime, currentTime, on groups, pausing and playing groups
Seems to be working.

Share player prototype with group players. Combine play() code for both types of groups.

Fixed some breaking tests

Small cleanup

Reverse() for groups sort of works. Going to change _startOffset
to be absolute, not relative to the parent.

Alternate offsets seem to be working

Comments

Comments

Cleanup.

Changed play

Changed the way group players are made. Reversing works
repeatedly on groups now, but probably won't work if
the group has a start delay (or its start time isn't
0 for some other reason).

Change the way player.play calculates startTmie

offsets for reverse.
Fix failing unit tests.
Cleanup
Remove set playbackRate from Player.
Merge pull request #61 from rjwright/Groups

WIP - Improvements to groups