Similaritymeasures

Changed
- Fix paper citation had the incorrect month and year.

Changed
- There was bug in testing for a complex quadrilateral that made me incorrectly change the is_simple_quad function. This bug has existed in the area function since August, and should be fixed now. Thanks to aanchalMongia for the detailed report in https://github.com/cjekel/similarity_measures/issues/7 .

Changed
- Fix bug in simple quad check; simple quads occur with two or four positive cross products, or with two or four negative cross products.

Added
- setuptools is now a requirement
- online docs [here](https://jekel.me/similarity_measures/index.html)
Changed
- Fréchet distance now uses an iterative dynamic programming algorithm (Thanks to Sen ZHANG https://github.com/SenZHANG-GitHub). The performance improvements were briefly studied in this [notebook](https://github.com/cjekel/similarity_measures/blob/master/frechet_distance_recursion_vs_dp.ipynb).

Changed
- fixed bug in is_simple_quad(), which would sometimes return the incorrect value
- fixed bug in pcm() when a and b where swapped based on arc_length

Changed
- fixed broken links in README !