Added JsonMatcher (#153)

src/WireMock.Net/Matchers/IValueMatcher.cs

@@ -0,0 +1,15 @@
+namespace WireMock.Matchers
+{
+    /// <summary>
+    /// IValueMatcher
+    /// </summary>
+    /// <seealso cref="IObjectMatcher" />
+    public interface IValueMatcher: IObjectMatcher
+    {
+        /// <summary>
+        /// Gets the value.
+        /// </summary>
+        /// <returns>Value</returns>
+        string GetValue();
+    }
+}