patch for non-zero single digit ip v4 addresses

I initially tested the `is-ip` module which failed on an IP address (v4) which started with a single digit, e.g. `4.12.45.34`, so for something real like Google's DNS server `8.8.8.8` this would fail. I have updated both `index.js` to take this into account and also the `test.js` file with a test for `8.8.8.8` which initially failed prior to this patch, so this would fix `is-ip` too.