strings: Include SPACE in the regexp in strings

The previous regular expression that was used in strings didn't match
the SPACE character. This commit makes strings behave a little more like
GNU strings.
strings: Better matching of IPs

This commit fixes a bug, where strings wouldn't correctly match IPs.
Merge pull request #171 from Erethon/feature-strings-regex

strings: Fix a bug with IP matching and make strings behave more like GNU strings