Adding CacheEntry to be used by the APIClient cache

src/main/java/com/cloudius/urchin/api/CacheEntry.java

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2015 Cloudius Systems
+ */
+
+package com.cloudius.urchin.api;
+
+public class CacheEntry {
+    long time;
+    public String value;
+
+    CacheEntry(String value) {
+        time = System.currentTimeMillis();
+        this.value = value;
+    }
+
+    public boolean valid(long duration) {
+        return (System.currentTimeMillis() - time) < duration;
+    }
+
+}