Several fixes in setup.py and core.py

[rcannood]

Hello @ManuSetty and @iandriver,

During our usage of Wishbone, we fixed several small issues.

• Install phenograph a bit later (46f8338)
• Install Cython earlier (cdbebf5)
• Require matplotlib>=2.0 (89c7698)
• Import csgraph from scipy.sparse (7c869ce)
• Convert tailk and I to integers, as errors were being produced that they were numpy floats (88e89a9)

For our own usage, we preferred if wishbone did not create any directories in our home directory (f66b7ca). However, for this pull request we reverted this commit (b706ded) as downstream analyses might depend on the existence of this folder.

Kind regards, @Zouter and @rcannood

[ManuSetty]

Thank you very much for your contributions - I appreciate this very much! The home directory additions are necessary for some downstream analyses.