remove srcd.works dependency

[alcortesm]

Part of https://github.com/src-d/backlog/issues/700.

[codecov]

Codecov Report

Merging #156 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #156   +/-   ##
=======================================
  Coverage   81.29%   81.29%           
=======================================
  Files          16       16           
  Lines        3400     3400           
=======================================
  Hits         2764     2764           
  Misses        433      433           
  Partials      203      203

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