Adding json extension example

gradle-jtwig-json-extension-simple/build.gradle

@@ -0,0 +1,20 @@
+group 'org.jtwig'
+version '1.0'
+
+apply plugin: 'java'
+
+sourceCompatibility = 1.7
+
+repositories {
+    mavenLocal()
+    mavenCentral()
+    jcenter()
+    maven {
+        url "http://dl.bintray.com/jtwig/maven"
+    }
+}
+
+dependencies {
+    compile "org.jtwig:jtwig-json-extension:1.+"
+    compile "com.fasterxml.jackson.core:jackson-databind:2.5.3"
+}

gradle-jtwig-json-extension-simple/settings.gradle

@@ -0,0 +1,2 @@
+rootProject.name = 'gradle-jtwig-json-extension-simple'
+

gradle-jtwig-json-extension-simple/src/main/java/org/jtwig/example/json/SimpleJsonApp.java

@@ -0,0 +1,45 @@
+package org.jtwig.example.json;
+
+import org.jtwig.JtwigModel;
+import org.jtwig.JtwigTemplate;
+import org.jtwig.environment.EnvironmentConfiguration;
+import org.jtwig.environment.EnvironmentConfigurationBuilder;
+import org.jtwig.json.JsonExtension;
+
+public class SimpleJsonApp {
+    public static void main(String[] args) {
+        EnvironmentConfiguration configuration = EnvironmentConfigurationBuilder.configuration()
+                .extensions().add(JsonExtension.defaultJsonExtension()).and()
+                .build();
+        JtwigTemplate jtwigTemplate = JtwigTemplate.inlineTemplate("{{ json_encode(variable) }}", configuration);
+        JtwigModel jtwigModel = JtwigModel.newModel().with("variable", new Model(
+                "My Name", 30, "Committer"
+        ));
+
+        System.out.println(jtwigTemplate.render(jtwigModel));
+    }
+
+    private static class Model {
+        private final String name;
+        private final int age;
+        private final String group;
+
+        public Model(String name, int age, String group) {
+            this.name = name;
+            this.age = age;
+            this.group = group;
+        }
+
+        public String getName() {
+            return name;
+        }
+
+        public int getAge() {
+            return age;
+        }
+
+        public String getGroup() {
+            return group;
+        }
+    }
+}