Use ASCII digits in port number parsing

[zopieux]

Currently, bleach accepts (linkyfies) the following “URLs”:

• http://foo.com:𝟠𝟘𝟠𝟘/
• http://foo.com:٣٩٩٩/

That is because the \d modifier of Python unicode regular expressions matches all digits in the Nd block (search for category [Nd] here), and there are many things in there.

This PR replaces \d with [0-9]+ and two test URLs to assert these links are not recognized.

Note: an alternative would be to use the re.ASCII flag but:

• it's hard to be compatible with Python 2
• it may not be appropriate because we do want to match funky unicode chars in other parts of the URL

Note: funnily enough, GitHub-flavored markdown also linkyfies them! http://foo.com:𝟠𝟘𝟠𝟘/

[willkg]

Tossing this in the v1.5 milestone. I'll look through it next week.

[willkg]

I broke this when I switched to py.test. I fixed the commit in PR #225. Closing this out in favor of that one.