Enable Delaunay Triangulation

Adds a method to shapely.ops to perform Delaunay triangulation on a geometry,
return a list of geometries.
Add some tests for Delaunay triangulation.

Skip if GEOS version doesn't support it.
Add GEOS 3.4 class.

Adds new class for GEOS 3.4 and move the Delaunay triangulation method
there.
Merge pull request #134 from jwass/triangulate

Enable Delaunay Triangulation