Support kwargs style parameters passing in TSimpleServer

[aisk]

kwargs is supported in TThreadedServer, so I think TSimpleServer should support it too.

[codecov]

Codecov Report

Merging #67 into master will not change coverage.
The diff coverage is 50%.

@@           Coverage Diff           @@
##           master      #67   +/-   ##
=======================================
  Coverage   80.57%   80.57%           
=======================================
  Files          35       35           
  Lines        3480     3480           
=======================================
  Hits         2804     2804           
  Misses        676      676

Impacted Files	Coverage Δ
thriftpy2/server.py	37.83% <50%> (ø)	⬆️

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[ethe]

Yeah it should be, thank you!