If protocol is not found, validProtocols still matches

Example string: "Juhasz (@tibor) (2 days ago) <Debug Information> postid:A9fHY8gbEm9; percent done:0%; activityCount: 0;"
The reggex matches "postid:A9fHY8gbEm9" as a correct link, since the regex allows "protocol:page" style (http://daringfireball.net/2010/07/improved_regex_for_matching_urls) as mentioned in pull request #76. 

In determineLinks, `NSRange protocolRange = [link rangeOfString:@"://"];` fails to find a protocol but since the protocol sting is initialized to "http", `[_validProtocols containsObject:protocol.lowercaseString]` always matches.
fix for protocol match

regex matches “protocol:page” style, but `protocolRange` searches for
“protocol://page“.
added test for non valid protocols
Merge pull request #120 from adamjuhasz/master

If protocol is not found, validProtocols still matches