[skip travis] DOC: Update instructions in README.md for developers.

[shaneahmed]

• Update instructions in README.md for developers.

[codecov]

Codecov Report

Merging #198 (f39a633) into develop (866c603) will not change coverage.
The diff coverage is n/a.

❗ Current head f39a633 differs from pull request most recent head 43aa51f. Consider uploading reports for the commit 43aa51f to get more accurate results

@@           Coverage Diff            @@
##           develop     #198   +/-   ##
========================================
  Coverage    99.79%   99.79%           
========================================
  Files           47       47           
  Lines         3909     3909           
  Branches       646      646           
========================================
  Hits          3901     3901           
  Misses           2        2           
  Partials         6        6           

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