[blackd] support HTTPS option

[alfozan]

I have a blackd service running behind https (i.e. https://blackd.com). Currently sublack uses http only. It'd be nice to have a config (i.e. black_blackd_https=True) for https here: https://github.com/jgirardet/sublack/blob/master/sublack/blacker.py#L106

Thank you!

[danpalmer]

FYI, you may want to edit the example you've given. May not be the best thing for people to open at work.

[alfozan]

FYI, you may want to edit the example you've given. May not be the best thing for people to open at work.

No worries; the example I provided is hypothetical