add test case about broken regex matching

[purpleidea]

I discovered a situation where the regex does not match correctly. The problem is that a regex like:

/[a-z]([a-z0-9:]*[a-z0-9]+)?/

can match a string (as quoted) with a trailing colon like:

"example42:"

Unfortunately this is wrong. This adds a test case which should pass when this bug is fixed.

Discussion exists in: https://github.com/blynn/nex/issues/50

[purpleidea]

w00t! Awesome! This helps a lot, thanks!