Use of setup_requires breaks offline build process

[ezaquarii]

Automat uses setup_requires, which is obsolete, broken and discontinued mechanism of supplying build-time dependencies. The main issue is that package build started as a subprocess of other build cannot derive dependencies location supplied in initial build process, thus completely breaking off-line builds (CI, package builders, isolated enterprise build farms, etc).

Recommended way of dealing with build-time dependencies is PEP 518, which is simply a TOML file listing the dependencies: https://www.python.org/dev/peps/pep-0518/

[glyph]

Looks like this is a part of #143 ?