Pygenometracks

* add the ability to control alpha of bedgraph tracks (thanks to mikewolfe)
* add GTF support (thanks to lldelisle)
* add support for various BED flavors (thanks to lldelisle)
* adopt codebase to lastest matplotlib changes (thanks to lldelisle)
* various new tests, code cleanups and smaller fixes all over

- support for Python 2 has been removed.
- regions smaller than 200000 can be plotted with a warning message for plotting TADs.
- non existing chromosomes in some or all of the input files can be asked as regions to plot the tracks.

* Support for epilogos 38
* HiC improvements and migration to use [HiCMatrix](https://github.com/deeptools/HiCMatrix). Thanks to *joachimwolff* for these changes.
* Different coloring of negative and positive bigwig values is now possible. Thanks to *Phlya* for this improvement.

This release makes it **very easy to add new tracks*! See the Readme for examples on how to do that.

Furthermore, this release:

* Adds Hi-C tracks
* Allows a track be plotted over the previous. There is not limit on the tracks that can be plotted on top of each other
* Removed unnecessary empty space around the resulting image
* Enlarged the README.md file with new examples and a mini-tutorial on how to add new tracks.
* Added chromosome name and title to x-axis plot
* Added option to plot links as 'triangles'. This is useful to overlay links with Hi-C data to identify the contact pixel.
* Added line width to bed track
* Added 'bed graph' track
* Added a track that can plot .narrowPeaks

This version added python3 compatibility to the code