First test compile OK

examples/MQ4/MQ4.ino

@@ -0,0 +1,12 @@
+#include <MQUnifiedsensor.h>
+
+
+void setup() {
+  // put your setup code here, to run once:
+
+}
+
+void loop() {
+  // put your main code here, to run repeatedly:
+
+}