Add a "Troubleshooting" section to installation docs

[jdufresne]

This section describes MIME type issues on some platforms when using the
Django runserver command.

Fixes #1352

[codecov]

Codecov Report

Merging #1383 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1383   +/-   ##
=======================================
  Coverage   87.83%   87.83%           
=======================================
  Files          29       29           
  Lines        1578     1578           
  Branches      222      222           
=======================================
  Hits         1386     1386           
  Misses        141      141           
  Partials       51       51           

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[matthiask]

Thanks. This is helpful.