Correting way to call async

[uasouz]

On Python 3.7 async is a reserved keyword,so i used getattr() to get it

[codecov-io]

Codecov Report

Merging #13 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master      #13   +/-   ##
=======================================
  Coverage   75.92%   75.92%           
=======================================
  Files           5        5           
  Lines         324      324           
=======================================
  Hits          246      246           
  Misses         78       78

Impacted Files	Coverage Δ
wsstat/clients.py	70.65% <0%> (ø)	⬆️
wsstat/demo.py	47.82% <0%> (ø)	⬆️

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[coveralls]

Coverage remained the same at 75.926% when pulling c52f24b on uasouz:master into 58c7d33 on Fitblip:master.

[Fitblip]

Interesting, thanks for the PR! Not sure why travis/codecov barfed here, but this should be good to merge once I make sure tests are passing 👍

[Fitblip]

Yeah this looks good. I'll merge and cut a new release, thanks!