IdnaConvert::decode() fails to convert simple domain name

[cerlestes]

$converter = new IdnaConvert();
$converter->decode('xn--zcaj8cya.bar.baz');

The above code will fail with the following exception: This is not a punycode string

This is because it's pushing every domain part into Punycode::decode(), which will raise the aforementioned exception when the provided string (bar in this case) is not punycoded.

Imho parse_url() shouldn't be used within the decode() method. There should be a separate decodeUri() method, to reflect how encoding is handled. And of course the exception must be handled within the IdnaConvert class, i.e. just ignoring it and using the input string.

[cerlestes]

I've created two pull requests now. #8 is backwards-compatible and just adds more checks to the current code. #7 is a breaking change, that modifies the public API (one constant removed, one exception removed) and removes unnecessary (and bad-quality) code.