* Quiet OpenSSL deprecation warning

Future is calling installation endless recursion. We are only
using it for an html.escape method, so we make our own and get
rid of future.

Related-Bug: #6

This is for the sake of getting something out there, including
fixes to get stuff working with Python 3.7.

We'd like to have a stable location for documentation. The
destination will be https://pythonpaste.readthedocs.io

This change also tries to make sure that there are sufficient
warnings throughout about the status of Paste.

pytest exposes many warnings, some but not all of which are cleaned
up here. The main switch is to use html.escape instead of cgi.escape.
This inspired the addition of 'future' to requirements.

The remaining warnings are related to pytest deprecations or over-eager
test discovery.

It is perhaps ironic that the switch to pytest is to avoid nose being
mostly dead, and now we are using features in pytest that pytest wants
to make dead. These are left for later cleanups, which means that
running the tests is noisy.