Created IPathway interface and changed users of Pathway to use IPathway instead

Previously, all pathway code was based on the abstract class "Pathway." Because it is an abstract class, rather than an interface, it made it difficult for objects that already derive from another class (e.g. MonoBehaviour) to provide pathway information.

Switching to an interface allows those classes to implement the required methods without losing their existing base class relationship; and because the Pathway class itself supports the interface, no existing code should be affected.
Merge pull request #3 from richard-fine/master

Created IPathway interface and changed users of Pathway to use IPathway instead
UnitySteer 2.5b1. Merging development changes
UnitySteer 2.5.b3. Merging development changes
UnitySteer 2.5b4. Merging development changes

I have been using 2.5b4 on Hairy Tales for months with only minor
changes and fixes, so it's close enough to stable that this will
likely be the last beta before 2.5 proper.  Interfaces are likely
to remain stable.
Merge branch 'release/2.5'
Add missing EditorGUILayout.EndVertical() call
Merge pull request #17 from Simie/master

Add missing EditorGUILayout.EndVertical() call
Merge branch 'master' into development
Updated priority queue to allow pausing
Disabling SteerForPoint when defaulting to our current position

Otherwise SteerForPoint would interfere with any other behaviors by
insisting that the vehicle return to its origin.
Fixed mistaken Biped reference