Correctly parse ImageMagick bottle version

Commit 2695821e98 ("Only use the bottle if its version is up-to-date")
essentially broke the ImageMagick bottle, because the version parsing
logic returns "1" as the bottle version.

Fixing this requires only a slight modification to the bottle URL regex;
includes a test.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>