PyPI page improvements

[villares]

I don't know how to help fix this, but the main image on the PyPI page is broken and the contribution guidelines link is also broken. Both might be related to some transformation the README.md suffers to become the description in pypi.org. Also, I believe it would be great if there was a link to this repository (https://github.com/quant-sci/compute-geometry) or a documentation site. No project homepage link is provided there.