Instantiate errorInfo NSMutableDictionary using mutableCopy as suggested by Elshad. close #125.

Author: beepscore

SocketIO.m

@@ -676,7 +676,8 @@ - (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:NSLocalizedDescriptionKey] mutableCopy];
 
         NSError *err = [NSError errorWithDomain:SocketIOError
                                            code:SocketIOHandshakeFailed