Follow XDG Base Directory Specification

[FalcoGer]

It'd be really nice if the program didn't pollute the home directory if a XDG directory for configuration files is available, typically ${HOME}/.config and place the config file there. This reduces clutter in the home directory.
Same for the log output and such.

[rolandwalker]

Mycli does read config files if stored in ~/.config/mycli/myclirc. This is just underdocumented!

[sentosango]

Because mycli still initially creates the ~/.myclirc config, then this still cannot be considered as following the XDG specification.

Correct behavior:

• read ~/.config/mycli/myclirc
• read ~/.myclirc (fallback)
• create default ~/.config/mycli/myclirc

Stop at the first "successful" step.