Added social media mailing list & gitter channel

[story645]

Added the mailing list for the social media contributors

[story645]

thansk for your approvals @timhoffm and @dopplershift, I updated this to include the gitter channel too since that seemed more sensible than opening a new PR that I'd have to rebase on this one anyway

[timhoffm]

I'm unclear what the merge policies here are. I'd say this is doc-like,so one approval is enough. OTOH these are the governance docs which maybe need a majority of the steering council?

[story645]

Yeah I put this doc in this repo before the 3 merge rule and #24 is to move it out but the repo to put it in doesn't exist yet. I agree that this should be mergeble with one approval.

Frankly I'm uncomfortable w/ the fact that technically the communications lead (community manager since it's currently under that umbrella) doesn't even have to be looped into changes on this doc, given they'd be the one charged w/ implementing any new policies. And yes I wrote this doc so that's on me, but now I'm unsure how a PR making that clear would be received.

[dopplershift]

@story645 I'd be receptive to a PR clarifying it.