Use newer percent encoding method where available

Checks deployment target for compatibility

Closes #416

Author: billinghamj

JSONModel/JSONModelNetworking/JSONHTTPClient.m

@@ -120,13 +120,20 @@ +(NSString*)urlEncode:(id<NSObject>)value
     }
 
     NSAssert([value isKindOfClass:[NSString class]], @"request parameters can be only of NSString or NSNumber classes. '%@' is of class %@.", value, [value class]);
-        
+
+    NSString *str = (NSString *)value;
+
+#if __IPHONE_OS_VERSION_MIN_REQUIRED >= __IPHONE_7_0 || __MAC_OS_X_VERSION_MIN_REQUIRED >= __MAC_10_9
+    return [str stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]];
+
+#else
     return (NSString *)CFBridgingRelease(CFURLCreateStringByAddingPercentEscapes(
                                                                                  NULL,
-                                                                                 (__bridge CFStringRef) value,
+                                                                                 (__bridge CFStringRef)str,
                                                                                  NULL,
                                                                                  (CFStringRef)@"!*'();:@&=+$,/?%#[]",
                                                                                  kCFStringEncodingUTF8));
+#endif
 }
 
 #pragma mark - networking worker methods