Configuration file

[guibou]

krank command line may now have a lot of options (such as all the api key needed for github and gitlab instances) which are painful to set to each call, so we need a configuration file.

I'm wondering about the design. Should the configuration be by project or global? I can totally imagine a global .config/krank.conf containing something like:

[issue-tracker-keys]
github.com=foo
gitlab.com=bar
gitlab.haskell.org=biz

[guibou]

cc @gbataille