Render long description as ReST

[A5rocks]

Currently https://pypi.org/project/trio/ renders weirdly. I haven't tested this actually fixes it but I do believe it does.

[codecov]

Codecov Report

Merging #2674 (2fe3662) into master (afd51d1) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2674   +/-   ##
=======================================
  Coverage   98.84%   98.84%           
=======================================
  Files         114      114           
  Lines       16514    16514           
  Branches     3003     3003           
=======================================
  Hits        16323    16323           
  Misses        134      134           
  Partials       57       57           

[jakkdl]

I have no insight here, so unless others do feel free to merge and see if it fixes it.

[A5rocks]

Oh I can probably test this on test.pypi.org. I'll do that soon:tm:.

[A5rocks]

Looks like it works! https://test.pypi.org/project/A5rocks-trio/0.22.0/ (...for some reason trio wasn't taken on test.pypi.org but I decided I didn't want to pollute it like that so to pseudo-namespacing I go!)

[A5rocks]

I'm just going to merge this in cause it's proven itself on testpypi.