add get_json method to request handler
add get_json method to request handler

steal from flask

luastoned/turbo,mniestroj/turbo,YuanPeir-Chen/turbo-support-mipsel,kernelsauce/turbo,ddysher/turbo,YuanPeir-Chen/turbo-support-mipsel,zcsteele/turbo,ddysher/turbo,zcsteele/turbo,luastoned/turbo