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/require/__snapshots__/jsfmt.spec.js.snap

@@ -74,7 +74,8 @@ require(\"not a module name\");
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // @flow
 
-function require() {}
+function require() {
+}
 require(\"not a module name\");
 "
 `;
@@ -131,8 +132,10 @@ require.call(null, \"DoesNotExist\");
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 /* @flow */
 
-function takesANumber(num: number): void {}
-function takesAString(str: string): void {}
+function takesANumber(num: number): void {
+}
+function takesAString(str: string): void {
+}
 
 // @providesModule
 var A = require(\"A\");