Port anitya to use urllib2 instead of python-requests

The problem of python-requests is that it does not support calls to ftp
servers. We have a number of projects using FTP and providing FTP urls.

The problem with urllib and urllib2 is that neither actually check if
the SSL certificate is valid or matching the hostname.
Unfortunately, we'll have to do without for two reasons: a) too many
projects are FTP based and b) there is no option in the UI (for the
moment) to disable that SSL check.
Try to use urllib2 only for FTP URLs

This should allow us to still benefit from python-requests' SSL cert check
on http URLs.
Fix unit-tests suite for new upstream versions
Let's make sure the url is specifying the ftp or ftps protocol
Merge pull request #13 from fedora-infra/port_urllib

Port urllib