adds NewClientFromPool and Close methods. includes example

[filipecosta90]

fixes #61 and #10

[codecov]

Codecov Report

Merging #62 into master will decrease coverage by 1.36%.
The diff coverage is 68.75%.

@@            Coverage Diff             @@
##           master      #62      +/-   ##
==========================================
- Coverage   82.46%   81.09%   -1.37%     
==========================================
  Files           6        6              
  Lines         439      455      +16     
==========================================
+ Hits          362      369       +7     
- Misses         39       46       +7     
- Partials       38       40       +2     

Impacted Files	Coverage Δ
pool.go	80.43% <54.54%> (-13.86%)	⬇️
client.go	87.35% <100.00%> (+0.37%)	⬆️
common.go	86.20% <0.00%> (-6.90%)	⬇️

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