New class structure
There is a new class-structure in `server-info` utility and `netutils_linux_hardware` package:
Server class manages five subsystems - CPU, Disk, Net, Memory and System.
Server (server-info) can collect (--collect), read (--show) and rate (--rate) data.
Before the refactoring there were 3 big classes: Reader, Parser (--show) and Assessor (--rate). They had duplicated data about subsystems. Well, there were no "subsystems", there were just a lot of functions with prefixes in those classes. Now all those functions live in their own subsystems, all subsystems have standardised API (that's very cool for Server class, it can just iterate over subsystems).
Folding
There is a new `Folding` class with all the folding logic/constants. Also there is no more -f, -ff, -fff args, use --device, --subsystem, --server instead.
Other things
Some code was simplified and I restored run tests for `server-info --rate`. Also I got rid of `six.iteritems` dependency in few places and just use .items(). There no big data, so I don't think that 2-3 kbits of RAM are more than code simplicity.