Fixed binding issue where  was binding to the  in the let expression rather than the parameter.
Scaling was not accounting for range -1 to 1.
Reverted back to a and b and switched internal b to base.
Merge pull request #7 from jcollard/random-lo-hi-bindings

Fixed binding issue where  was binding to the  in the let expression rat...
Move runtime into core
Have Element.update return the new node