[v1.0.1] Fix bug in "is edge flip required' test

Overview

Bug-fix release: fix an error in code that tests if an edge flip is required.
Issue: #37
Fixing PR: #38

Fix Details

Previously flip was rejected only if both vertices of flip-candidate edge belong to the super-triangle.
This sometimes resulted in wrong edges and incorrect convex-hull.
The change: instead reject the edge-flip if

• at least one flip-candidate edge's vertex belongs to super-triangle
• original edge does not touch super-triangle.

If the case when both original edge and flip-candidate edge touch super-triangle use normal circumcircle test as a tie-breaker.

Two test files for regression testing are added.