Fix typo in README.md

[jlmcdonnell]

No description provided.

[codecov]

Codecov Report

Merging #73 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master      #73   +/-   ##
=========================================
  Coverage     68.11%   68.11%           
  Complexity       82       82           
=========================================
  Files            11       11           
  Lines           367      367           
  Branches         24       24           
=========================================
  Hits            250      250           
  Misses          103      103           
  Partials         14       14

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[rogerhu]

Thanks!