Added static keyword

Author: jaaufauvre

src/main/java/com/mastercard/developer/json/JsonEngine.java

@@ -56,7 +56,7 @@ private static boolean isClassFound(String className) {
         }
     }
 
-    protected Object asPrimitiveValue(String string) {
+    protected static Object asPrimitiveValue(String string) {
        // Boolean?
         if ("true".equals(string) || "false".equals(string)) {
             return Boolean.valueOf(string);
@@ -66,14 +66,13 @@ protected Object asPrimitiveValue(String string) {
         try {
             return Long.valueOf(string);
         } catch (NumberFormatException e) {
-            // Do nothing
+            // Not a number, do nothing
         }
 
         // String
         return string;
     }
 
-
     public String toJsonString(Object object) {
         if (null == object) {
             throw new IllegalStateException("Can get a JSON string from a null object!");
@@ -84,7 +83,6 @@ public String toJsonString(Object object) {
         return getJsonProvider().toJson(object);
     }
 
-
     protected boolean isJsonPrimitive(Object jsonElement) {
         JsonProvider jsonProvider = getJsonProvider();
         return !jsonProvider.isMap(jsonElement) && !jsonProvider.isArray(jsonElement);