Use io.open() for receive buffering.
Use io.open() for receive buffering.

~10% performance gain on Python >2.7

boneyao/PyMySQL,anson-tang/PyMySQL,nju520/PyMySQL,methane/PyMySQL,wraziens/PyMySQL,lzedl/PyMySQL,modulexcite/PyMySQL,lzedl/PyMySQL,DashaChuk/PyMySQL,Geoion/Tornado-MySQL,NunoEdgarGub1/PyMySQL,PyMySQL/PyMySQL,aio-libs/aiomysql,pulsar314/Tornado-MySQL,Ting-y/PyMySQL,jheld/PyMySQL,PyMySQL/Tornado-MySQL,yeyinzhu3211/PyMySQL,jwjohns/PyMySQL,xjzhou/PyMySQL,MartinThoma/PyMySQL,pymysql/pymysql,xjzhou/PyMySQL,eibanez/PyMySQL,yeyinzhu3211/PyMySQL,mosquito/Tornado-MySQL,wraziens/PyMySQL,eibanez/PyMySQL