-------------------------------------------------------------------------------
   Computes the area of a triangle mesh.
-------------------------------------------------------------------------------
   Form:
   a = AreaTriMesh( v, f )
-------------------------------------------------------------------------------

   ------
   Inputs
   ------
   v               (:,3)  Vertices
   f               (:,3)  Faces

   -------
   Outputs
   -------
   area            (1,1)  Area

-------------------------------------------------------------------------------