Demonstrates Android HTTPS via urllib module

[AndreMiras]

Creates a unit test that shows setting SSL_CERT_DIR is mandatory.
Refs kivy/python-for-android#1827

Running the app on Android should produce the following output:

06-08 02:30:30.302 30934 31115 I python  : Android kivy bootstrap done.
__name__ is __main__
06-08 02:30:30.302 30934 31115 I python  : AND: Ran string
06-08 02:30:30.302 30934 31115 I python  : Run user program, change dir
and execute entrypoint

06-08 02:30:31.094 30934 31115 I python  : [WARNING] [Config      ]
Older configuration version detected (0 instead of 21)
06-08 02:30:31.094 30934 31115 I python  : [WARNING] [Config      ]
Upgrading configuration in progress.
06-08 02:30:31.103 30934 31115 I python  : [INFO   ] [Logger      ]
Record log in
/data/user/0/org.httpsapp.httpsapp/files/app/.kivy/logs/kivy_19-06-08_0.txt
06-08 02:30:31.103 30934 31115 I python  : [INFO   ] [Kivy        ]
v1.11.0.dev0, git-d562ecc, 20190607
06-08 02:30:31.103 30934 31115 I python  : [INFO   ] [Python      ]
v3.7.1 (default, Jun  8 2019, 01:44:06)
06-08 02:30:31.103 30934 31115 I python  : [Clang 6.0.2
(https://android.googlesource.com/toolchain/clang 183abd29fc496f55
06-08 02:30:31.120 30934 31115 I python  :
/data/user/0/org.httpsapp.httpsapp/files/app/_python_bundle/site-packages/requests/models.py:176:
DeprecationWarning: Using or importing the ABCs from 'collections'
instead of from 'collections.abc' is deprecated, and in 3.8 it will stop
working
06-08 02:30:31.581 30934 31115 I python  :  ..
06-08 02:30:31.582 30934 31115 I python  :
----------------------------------------------------------------------
06-08 02:30:31.582 30934 31115 I python  :  Ran 2 tests in 0.467s
06-08 02:30:31.583 30934 31115 I python  :
06-08 02:30:31.584 30934 31115 I python  :  OK

[AndreMiras]

So yes I've adopted a different approach than the initial demo app.
Here I'm documenting the bug/feature via unit tests. I show that it's expected to fail without loading the environment variable. Then I later show it's working while loading it.
If you prefer the demo app approach it's also fine 👍