Move overlap functions in geometry package
Adding __init__.py for geometry subpackage
Change aperture.py to use geometry sub-package
Removing duplicate functions
Place for geometry docs
Adding more docs to circular_overlap_grid
Adding more docs to elliptical_overlap_grid
Adding __all__
adding calling sequence
Changing link
Merge pull request #99 from bsipocz/create_geometry_package

Create geometry sub-package