Connector: remove dependency on requests library

[peiwangdb]

Remove the installation dependency on requests library and modify the code accordingly.
Example: chang:

import requests
requests.get("www.python.org").json()

to:

import http.client
import json
conn = http.client.HTTPSConnection("www.python.org")
conn.request("GET", "/")
r1 = conn.getresponse()
json.loads(r1.read())

[dovahcrow]

Close in favor of #396