add weixin received message parse
add weixin event parse
add weixin response message
add weixin sendCustomMessage
add weixin send custom message test& fix issues
fix weixin news message XML format
add return result for weixin sendCustomMessage
finish issue #3: add weixin getFollowers api
issue #3: fix endless loop when getFollowers due the weixin MP dont't
return a null/blank openid.
#3, fix next_openid parameter mistake
fix weixin tests