add support for WithTimeout and WithDeadline

[derekperkins]

This is just a convenience wrapper around context.WithTimeout/WithDeadline

[codecov]

Codecov Report

Merging #13 into master will decrease coverage by 0.76%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master      #13      +/-   ##
==========================================
- Coverage   21.71%   20.94%   -0.77%     
==========================================
  Files           6        6              
  Lines         327      339      +12     
==========================================
  Hits           71       71              
- Misses        246      258      +12     
  Partials       10       10

Impacted Files	Coverage Δ
request.go	17.29% <0%> (-1.11%)	⬇️
client.go	28.4% <0%> (-1.36%)	⬇️

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