Json fixes (#91) (#92)

* Fixes for JsonPath

* More tests

* Fixes + added tests

src/WireMock.Net/Matchers/IStringMatcher.cs

@@ -0,0 +1,21 @@
+namespace WireMock.Matchers
+{
+    /// <summary>
+    /// IStringMatcher
+    /// </summary>
+    public interface IStringMatcher : IMatcher
+    {
+        /// <summary>
+        /// Determines whether the specified input is match.
+        /// </summary>
+        /// <param name="input">The input.</param>
+        /// <returns>A value between 0.0 - 1.0 of the similarity.</returns>
+        double IsMatch(string input);
+
+        /// <summary>
+        /// Gets the patterns.
+        /// </summary>
+        /// <returns>Patterns</returns>
+        string[] GetPatterns();
+    }
+}