[mlpack] New mlpack chat services

[Ryan Curtin]

Hello there,

After the NumFOCUS summit, there was some discussion about additional
chat services, and I've spent some time playing with Matrix and setting
up various bridges.  I think most people who are in IRC have seen me
working on this (sorry for the lots of messages!), but anyway I think
it's ready to call stable.  So I've updated
http://www.mlpack.org/community.html to point out the four chat channels
that we have bridged together:

  * IRC via freenode: #mlpack; you can use webchat (the link), or set up
    an account on freenode and use a client of your choice.  (This is
    what was previously set up.)

  * Gitter: https://gitter.im/mlpack/mlpack; you will need a Github
    account.

  * Matrix: #mlpack:matrix.org; you will need to set up a matrix.org
    account and use a client such as Riot or others.

  * Slack: https://mlpack.slack.org; in order to create an account,
    you’ll need to use the auto-inviter to send yourself an invite:
    http://slack-inviter.mlpack.org:3000.

For now the logs are still through IRC at https://www.mlpack.org/irc/.
Maybe we can change that later to be through Matrix, but for now, what
we have works, so I don't see a reason to make a change (unless someone
wants to take the initiative!  Feel free!).

I hope everyone finds this useful. :)  If you know of another bridge
that we should set up and is supported through matrix.org, just let me
know.

Thanks!

Ryan

-- 
Ryan Curtin    | "More like a nonja."
ryan at ratml.org |   - Pops