Fix improper use of NSLocalizedDescriptionKey.

This commit fixes a typo where an underlying error (NSError object) was associated with NSLocalizedDescriptionKey that is expected to be NSString.

Author: insanehunter

SocketIO.m

@@ -676,7 +676,7 @@ - (void) connection:(NSURLConnection *)connection didFailWithError:(NSError *)er
     _isConnecting = NO;
 
     if ([_delegate respondsToSelector:@selector(socketIO:onError:)]) {
-        NSMutableDictionary *errorInfo = [NSDictionary dictionaryWithObject:error forKey:NSLocalizedDescriptionKey];
+        NSMutableDictionary *errorInfo = [NSDictionary dictionaryWithObject:error forKey:NSUnderlyingErrorKey];
 
         NSError *err = [NSError errorWithDomain:SocketIOError
                                            code:SocketIOHandshakeFailed