Pin to urllib3 to fix encoding issue

[t8y8]

This is a quick fix to the url encoding issue(s) we are seeing.

There was a change after urllib3 1.24.3 that starting force encoding all non safe characters (I believe it is urllib3/urllib3@5d52370 that caused the issue.

Testing done: clean venv, pip installed with this change and saw the pinned version installed

[t8y8]

tdoyle-mac2:server-client-python tdoyle$ python3 -m venv clean
tdoyle-mac2:server-client-python tdoyle$ . clean/bin/activate
(clean) tdoyle-mac2:server-client-python tdoyle$ pip install -e .
Obtaining file:///Users/tdoyle/Documents/py/server-client-python
Collecting requests<3.0,>=2.11 (from tableauserverclient==0.6.1+89.g730512d)
  Using cached https://files.pythonhosted.org/packages/51/bd/23c926cd341ea6b7dd0b2a00aba99ae0f828be89d72b2190f27c11d4b7fb/requests-2.22.0-py2.py3-none-any.whl
Collecting urllib3==1.24.3 (from tableauserverclient==0.6.1+89.g730512d)
  Using cached https://files.pythonhosted.org/packages/01/11/525b02e4acc0c747de8b6ccdab376331597c569c42ea66ab0a1dbd36eca2/urllib3-1.24.3-py2.py3-none-any.whl
Collecting chardet<3.1.0,>=3.0.2 (from requests<3.0,>=2.11->tableauserverclient==0.6.1+89.g730512d)
  Using cached https://files.pythonhosted.org/packages/bc/a9/01ffebfb562e4274b6487b4bb1ddec7ca55ec7510b22e4c51f14098443b8/chardet-3.0.4-py2.py3-none-any.whl
Collecting certifi>=2017.4.17 (from requests<3.0,>=2.11->tableauserverclient==0.6.1+89.g730512d)
  Using cached https://files.pythonhosted.org/packages/69/1b/b853c7a9d4f6a6d00749e94eb6f3a041e342a885b87340b79c1ef73e3a78/certifi-2019.6.16-py2.py3-none-any.whl
Collecting idna<2.9,>=2.5 (from requests<3.0,>=2.11->tableauserverclient==0.6.1+89.g730512d)
  Using cached https://files.pythonhosted.org/packages/14/2c/cd551d81dbe15200be1cf41cd03869a46fe7226e7450af7a6545bfc474c9/idna-2.8-py2.py3-none-any.whl
Installing collected packages: chardet, urllib3, certifi, idna, requests, tableauserverclient
  Running setup.py develop for tableauserverclient
Successfully installed certifi-2019.6.16 chardet-3.0.4 idna-2.8 requests-2.22.0 tableauserverclient urllib3-1.24.3
You are using pip version 18.1, however version 19.2.2 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
(clean) tdoyle-mac2:server-client-python tdoyle$ pip freeze
certifi==2019.6.16
chardet==3.0.4
idna==2.8
requests==2.22.0
-e git+https://github.com/t8y8/server-client-python.git@730512d8bdaf0b2ffa775c4d3cb951b4dde99873#egg=tableauserverclient
urllib3==1.24.3