BUG: Removed cause for increased interpolation error.

Applicable to modifying the range of supplied points so that they are
wrapped to the source points range.  Resulted in values to be
interpolated over being slightly different.  This difference becomes
amplified when interpolating values which are then different on a high
gradient.
Review actions taken
Merge pull request #1093 from cpelley/interp_refactor_anotherway

BUG: Removed cause for increased interpolation error.