Fix Windows Build

Following the release of vine 5.0.0a1 and py-amqp 5.0.0a1 the AppVeyor build started failing.

This happened since we were using python setup.py test in that environment instead of tox. That command installs dependencies using easy_install which apparently does not implement PEP-440. Therefore, it picks the latest available version although it is an alpha version unlike pip which requires the --pre option to install alpha versions.

An attempt was made to migrate that build environment to tox, but tox installs our extra dependencies such as pycurl which does not release wheels for Windows.

We can either:

• Create a tox environment for Windows which avoids installing any extras.
• Work our way to resolve each and every build issue of our dependencies.

[thedrow]

We probably need to remove curl from Windows CI altogether until pycurl/pycurl#569 is resolved.

[thedrow]

Fixed by #1083.