Add important note about build-essential

[ripper234]

No description provided.

[codecov-io]

Codecov Report

Merging #573 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #573   +/-   ##
=======================================
  Coverage   52.82%   52.82%           
=======================================
  Files         104      104           
  Lines       27661    27661           
  Branches     4736     4736           
=======================================
  Hits        14611    14611           
  Misses      13050    13050

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[braydonf]

LGTM, it may not be apparent that this would be the default behavior.

[braydonf]

Resolved with #729