Clarify dependencies

[abcoxyzide]

Hi, thanks for making this tool!

I installed wgbs_tools on our machine and tried to run the init_genome command. During setup & running, I found a few dependencies that need to be in the environment that's not mentioned in the markdown. Thought it might be useful for you & others to know.

They are:

• numpy module (python3)
• pandas module (python3)
• tabix / bgzip

[nloyfer]

Done. Thank you!