Updated to the latest UnitySteer, removed flat boids scene

I updated the scenes to match UnitySteer as of this commit:
http://github.com/ricardojmendez/UnitySteer/commit/3be5cbd3e1fc3a0bda7401865be0bdf3259573b7

The flat boids example was frankly not very good, so I've removed
it. No sense in having it clutter the list of scenes.
Added a scene of a vehicle climbing a slope

There are two approaches that work:

1) Adding a character controller
2) Adding a collider, optimally with the rigidBody's freezeRotation set
  to true.

The character controller approach is about 4x as expensive as the simple
rigidbody, with the disadvantage that while the character controller
"just" climbs the slope, the rigidbody one needs enough speed to be
able to surmount it.
Added sample scene for SphericalObstacleData
Updating examples for UnitySteer 2.2
Updating to UnitySteer 2.5b1

WARNING: The scenes have not been fully tested or updated. Consider this
a work in progress.  Scenes are likely to be broken until this is tagged
as 2.5 final.
Sample scene updates (WIP)

- Replaced Biped references on several scenes for AutonomousVehicle
  (they had been left over as Biped during the previous class rename)
- New SphericalAvoidanceKitten prefab. I'm still working on the
  behavior.
- Sample scene for SteerToFollow.
Updating vcs references for Unity 3.5
Updating boid prefabs to take the new comfort distance into account
Test scene re-organization, updating references to UnitySteer 2.6dev

We no longer need TickedPriorityQueue independent from UnitySteer,
since it'll be included with the code.

Imported project on Unity 4.
Removed unused classes
Forcing asset serialization to text