This is a fairly ugly hack to temporarily work around the issue #10.
Until now Rust doesn't support so-called zone-ids[1] in link-local IPv6
socket-addresses and has a pending RFC on this topic. As I'm
encountering this issue on one of my machines I decided to work around
this issue (for now) by removing the zone-id from the IPv6 address.
This won't harm any other cases as `regex.replace_all` simply returns
the input if the regex doesn't match:
```
>> extern crate regex;
>> let re = regex::Regex::new(r"^\[(?P<ip>[A-Fa-f0-9:]+)%(.*)\]:(?P<port>[0-9]+)$");
>> let rs = re.replace_all("fairly unrelated stuff", "[$ip]:$port");
>> rs
"fairly unrelated stuff"
```
Please note that (1) this regex isn't RFC-compliant[2] and is just a
heuristic to remove zone-ids that currently break this exporter and
(2) this is something that probably shouldn't be merged as-is. I mainly
pushed this since I needed a workaround for this issue (and others
probably too), but it may be better to wait for proper support from the
language.
[1] https://tools.ietf.org/html/rfc4007#section-11
