Added URLDecoding to verifier

src/test/java/org/scribe/model/VerifierTest.java

@@ -0,0 +1,21 @@
+package org.scribe.model;
+
+import static org.junit.Assert.*;
+
+import org.junit.*;
+
+public class VerifierTest
+{
+  @Test
+  public void shouldParse()
+  {
+    Verifier verifier = new Verifier("p8k%2BGIjIL9PblXq%2BpH6LmT9l");
+    assertEquals(verifier.getValue(), "p8k+GIjIL9PblXq+pH6LmT9l");
+  }
+
+  @Test(expected = IllegalArgumentException.class)
+  public void shouldThrowErrorForNullString()
+  {
+    new Verifier(null);
+  }
+}