[DOC] Update links to user and developer help forums

[KirstieJane]

Summary

I was trying to find the right place to ask a question and these links were both broken so I figured I'd send a little PR to update the two places to ask questions as linked from the index bar.

updated: I've also done a quick search for other instances of the old mailing list link and updated those.

Additionally I've added the gitter and slack links. Happy to remove those if you don't want to provide so many options!

Please disregard this pull request if this isn't correct or helpful! Very happy to adapt anything that's needed.

List of changes proposed in this PR (pull-request)

Changed links:

• http://neurostars.org/t/nipype
  ---> https://neurostars.org/search?q=nipype
• http://projects.scipy.org/mailman/listinfo/nipy-devel ---> https://mail.python.org/mailman/listinfo/neuroimaging

Added links to

• https://gitter.im/nipy/nipype
• https://brainhack.slack.com/messages/C1FR76RAL

Acknowledgment

• I acknowledge that this contribution will be available under the Apache 2 license.

[codecov-io]

Codecov Report

Merging #2686 into master will increase coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2686      +/-   ##
==========================================
+ Coverage    67.6%   67.61%   +<.01%     
==========================================
  Files         340      340              
  Lines       43145    43145              
  Branches     5349     5349              
==========================================
+ Hits        29170    29172       +2     
+ Misses      13273    13271       -2     
  Partials      702      702

Flag	Coverage Δ
#smoketests	50.57% <ø> (ø)	⬆️
#unittests	65.1% <ø> (+0.02%)	⬆️

Impacted Files	Coverage Δ
nipype/utils/profiler.py	44.25% <0%> (+1.14%)	⬆️

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[KirstieJane]

A little ps: I'm working on a windows laptop and I can't install make so I haven't tested the docs build. Really sorry if they don't render properly 😞

[satra]

thank you @KirstieJane !

[satra]

and just as an fyi, circle does build the docs in this branch **ci/circleci: test_pytest **, so one can see the rendered docs (through the artifacts tab).

[KirstieJane]

Thanks @satra! I’m so sorry - I don’t really understand where to look for the rendered docs? Are they written to a GitHub branch or are they on the circle ci page? (I don’t know circle well so I’m searching a bit here!)

If it’s easy to ping a link to a rendered doc that would be mega helpful! No worries if you’re busy :)

[mgxd]

@KirstieJane on your build, you can click on the artifacts tab and expand the docs/ tree - here's a link to the main page

[KirstieJane]

Thank you @mgxd and @satra! The problem was that I wasn't signed in to circle ci - I can see most of the other tabs but not the artifacts one by just clicking the links you sent 😸 Once I logged in I could see that tab and all made sense ✨