Add changes to CHANGELOG.
Add changes to CHANGELOG.

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