Update readme with decodeTime docs for #65

[ryanatkn]

I love this library, thank you!

[codecov-io]

Codecov Report

Merging #66 into master will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #66   +/-   ##
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  Coverage   93.08%   93.08%           
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  Files           2        2           
  Lines         246      246           
  Branches       31       31           
=======================================
  Hits          229      229           
  Misses         17       17

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