Support client play handler / etc

[yutopp]

• Support client play handler
• More configurable Dialer
• Add tests/comments

[codecov]

Codecov Report

Attention: Patch coverage is 29.16667% with 102 lines in your changes missing coverage. Please review.

Project coverage is 55.49%. Comparing base (553a888) to head (ece6c5c).

Files	Patch %	Lines
client.go	29.62%	17 Missing and 2 partials ⚠️
message/net_stream.go	47.22%	12 Missing and 7 partials ⚠️
client_data_play_handler.go	0.00%	16 Missing ⚠️
message/net_connection.go	35.00%	8 Missing and 5 partials ⚠️
client_control_connected_handler.go	0.00%	12 Missing ⚠️
stream.go	0.00%	11 Missing ⚠️
message/body_decoder.go	50.00%	3 Missing and 3 partials ⚠️
stream_handler.go	37.50%	5 Missing ⚠️
message/error.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #60      +/-   ##
==========================================
+ Coverage   54.24%   55.49%   +1.24%     
==========================================
  Files          47       49       +2     
  Lines        2673     2786     +113     
==========================================
+ Hits         1450     1546      +96     
+ Misses       1052     1042      -10     
- Partials      171      198      +27     

Flag	Coverage Δ
unittests	55.49% <29.16%> (+1.24%)	⬆️

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