Add "VERIFY" to allow for self signed certs

[wetw0rk]

This feature should operate in a similar fashion to httpimport.INSECURE = True but instead httpimport.VERIFY = False to allow self signed certificates.

For example:

import httpimport

httpimport.VERIFY = False

with httpimport.remote_repo(['lib'], 'https://127.0.0.1'):
  from lib import thing