Model in simple_tess was wrong

west and east were switched. This caused a weird bug that only happened
when I started calculating the size differently.
Replace the check of EOF with fgets != NULL
Calculate size of the tesseroid with a greatcircle

The method used before is Ok for the equator but for the poles it is
very wrong! I'm using the Vicenty formula from
http://en.wikipedia.org/wiki/Great-circle_distance