Merge pull request #63 from nodemcu/dev094

merge Dev094
deal with uart.on api when required char number is 0
for set wifi issue 

dhcp client must be stop before setting station ip
build bins
Merge pull request #64 from alonewolfx2/patch-1

for set wifi issue
rebuild bin, add setip, setmac, sleeptype api to wifi module, fix #62