basic clap cli

[debris]

based on #185

uses clap cli

• cli is defined in cli.yml
• log level is set using --verbosity option instead of RUST_LOG env variable

[arkpar]

conflicted

[arkpar]

Have you seen this crate: https://github.com/docopt/docopt.rs? It uses a compiler plugin to generate args struct out of description, which is nicer than having a runtime parser and key-value access interface

[debris]

hmm... you may be right.
I will check it out.

[gavofyork]

I'm now working on a docopt PR.