token验证函数， 如果提示验证失败请检查1.你的url是否正确，2. 验证函数代码是否正确， 3.端口是否是80端口的， 4.返回值是否是echoster(4容易忽略)
def wxcsh_signature(form):
print form
signature = form['signature']
timestamp = form['timestamp']
nonce = form['nonce']
echostr = form['echostr']
print TOKEN, echostr
lists = [TOKEN, timestamp, nonce]
lists.sort()
hashcode = sha1(''.join(lists)).hexdigest()
if hashcode == signature:
print hashcode, signature
return echostr
return ''
