bump urllib3 version to 1.22
bump urllib3 version to 1.22

Resolves this import error when running pytest:

    ImportError while importing test module '/home/jhoblitt/github/sqre-codekit/tests/test_codetools.py'.
    Hint: make sure your test modules/packages have valid Python names.
    Traceback:
    tests/test_codetools.py:4: in <module>
        import codekit.codetools as codetools
    codekit/__init__.py:4: in <module>
        from .codetools import *  # NOQA
    codekit/codetools.py:13: in <module>
        from github3 import login
    venv/lib/python3.5/site-packages/github3/__init__.py:18: in <module>
        from .api import (
    venv/lib/python3.5/site-packages/github3/api.py:11: in <module>
        from .github import GitHub, GitHubEnterprise
    venv/lib/python3.5/site-packages/github3/github.py:13: in <module>
        from .auths import Authorization
    venv/lib/python3.5/site-packages/github3/auths.py:11: in <module>
        from .decorators import requires_basic_auth
    venv/lib/python3.5/site-packages/github3/decorators.py:11: in <module>
        from requests.models import Response
    venv/lib/python3.5/site-packages/requests/__init__.py:90: in <module>
        from urllib3.exceptions import DependencyWarning
    E   ImportError: cannot import name 'DependencyWarning'

lsst-sqre/sqre-codekit,lsst-sqre/sqre-codekit