fixed context manager __exit__ method, closes #1

__exit__ requires exc_type, exc_val, and traceback parameters, even if
they are not used
merge branch 'issue1' into devel
implemented __str__ method for geo and lamaz grids
merge branch 'issue2' into devel
added printing for sinusoidal, albers equal area grids
added grid attribute support
fedora 20 notes
Merge branch 'devel'