New IEnumerable to get the TickedQueue's items

Adding a way to iterate through the items, since I want to be able to
query them externally. Doing it as a IEnumerable to avoid exposing
direct access to the TickedQueueItem collection.
TickedQueue.Remove now has a success return value
BUGFIX: TickedQueue was ticking one item too many per update
New test for removing an item while it's enqueued
New TickedQueue.ExceptionHandler

Since TickedQueue ticks the items on its own, we can't really deal with
exceptions at the source unless we're notified.  Added a new exception
handler property.  TickedQueue will now catch exceptions and, if it has
a handler, notify it instead of throwing them.

Updated NUnit to 2.6.3
TickedQueue will not tick removed TickedQueueItems

Ran into an edge case with UnitySteer where a vehicle was being disabled
while the TickedQueue's work queue was being run through.  This had the
side effect that the item was removed from the main queue, but since it
was a "loop" item and already in the work queue, the Update method then
re-added it to the queue after ticking it.

Removing a TickedQueueItem from a queue will mark it as inactive. The
queue will now ignore inactive items.

Expanded tests.
New README
Fixing comment tags
Refactored TickedQueueItemComprarer.DefaultCompare, easier to debug
New isLooped parameter on TickedQueueItem constructor
Adding tickLength as a parameter on TickedObject constructor
Ensuring queue order on items with the same time and priority

We will now consider that if two items are inserted with the same time
and with the same priority, the second one in the comparison will be
considered the larger one.

Also:

- Fixed Timing test
- TestUnPausePriority wasn't marked as a test
Adding solutions, projects for VS2013
Merge pull request #3 from ricardojmendez/master

Multiple changes and improvements