Broken link in index.md

[geneorama]

During the review of pull request #20 I noticed a broken link in the notes of the main page, but it falls outside of the changes of the pull request

The https is missing the h

[^1]: Potash _et al._ (2015) [Predictive Modeling for Public Health](ttps://dssg.uchicago.edu/wp-content/uploads/2016/01/p2039-potash.pdf). _Proceedings of the 21th ACM SIGKDD International Conference on Knowledge Discovery and Data Mining_ pp. 2039-2047.

should be

[^1]: Potash _et al._ (2015) [Predictive Modeling for Public Health](https://dssg.uchicago.edu/wp-content/uploads/2016/01/p2039-potash.pdf). _Proceedings of the 21th ACM SIGKDD International Conference on Knowledge Discovery and Data Mining_ pp. 2039-2047.

[geneorama]

Moving to notes of pull request #20