Explicit Installation Dependencies

[alecandido]

2. I'm not fully happy about the "dependencies": they are a bit hidden inside the functions; nothing we need to deal now, but maybe I'd implement a very basic "dependency manager": a dictionary (containing mutual dependencies), and when start installing things we populate a list, and iterate over it to install stuffs sorted (it should be simple enough, but more explicit)

Originally posted by @alecandido in NNPDF/pinecards#152 (comment)