Remove Circle CI badge

[jednano]

for realz

[codecov]

Codecov Report

Merging #30 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master    #30   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           1      1           
  Lines          37     37           
  Branches        5      5           
=====================================
  Hits           37     37

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