Pool context option & stop with timeout

[alitto]

Changes included

• Added option to specify a parent context on a pool (pond.Context(parentCtx context.Context))
• Added method to stop the pool and wait until a given deadline is reached (StopAndWaitFor(deadline time.Duration)
• Migrated from Travis CI to Github Actions
• Fixed typos in comments
• Added a few sections to the Readme file

[codecov-commenter]

Codecov Report

Merging #24 (d67b1d5) into master (9d7bd8f) will increase coverage by 0.50%. The diff coverage is 96.55%.

@@            Coverage Diff             @@
##           master      #24      +/-   ##
==========================================
+ Coverage   98.57%   99.07%   +0.50%     
==========================================
  Files           2        2              
  Lines         210      325     +115     
==========================================
+ Hits          207      322     +115     
  Misses          3        3              

Impacted Files	Coverage Δ
pond.go	99.01% <96.55%> (+0.54%)	:arrow_up:
resizer.go	100.00% <0.00%> (ø)

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