Add newline for empty blocks {} (#205)

I find it weird to put `{}` together. So I figured I would change it to have an empty line and ask for feedback :)

![image](https://cloud.githubusercontent.com/assets/197597/21739279/062adc80-d44c-11e6-8bb7-5e0768f3ddde.png)

Beware: most of the test cases are not representative of real code, you almost never define blocks with no content in practice.

tests/async/__snapshots__/jsfmt.spec.js.snap

@@ -171,24 +171,42 @@ console.log(x.async);
 var async = 3;
 var y = { async };
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-async function f() {}
-async function ft<T>(a: T) {}
-
-class C {
-  async m() {}
-  async mt<T>(a: T) {}
-  static async m(a) {}
-  static async mt<T>(a: T) {}
+async function f() {
+}
+async function ft<T>(a: T) {
 }
 
-var e = async function() {};
-var et = async function<T>(a: T) {};
+class C {
+  async m() {
+  }
+  async mt<T>(a: T) {
+  }
+  static async m(a) {
+  }
+  static async mt<T>(a: T) {
+  }
+}
 
-var n = new async function() {}();
+var e = async function() {
+};
+var et = async function<T>(a: T) {
+};
 
-var o = { async m() {} };
-var ot = { async m<T>(a: T) {} };
-var oz = { async async() {} };
+var n = new async function() {
+}();
+
+var o = {
+  async m() {
+  }
+};
+var ot = {
+  async m<T>(a: T) {
+  }
+};
+var oz = {
+  async async() {
+  }
+};
 
 var x = { async: 5 };
 console.log(x.async);
@@ -236,7 +254,8 @@ async function foo2(): Promise<string> {
 }
 
 async function foo3(): Promise<string> {
-  function bar() {}
+  function bar() {
+  }
   return bar();
 }
 "