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/trailingComma/__snapshots__/jsfmt.spec.js.snap

@@ -11,7 +11,8 @@ a(
 
 a(\'value\', \'value2\', a(\'long-nested-value\', \'long-nested-value2\', \'long-nested-value3\'));
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-const a = (param1, param2, param3) => {};
+const a = (param1, param2, param3) => {
+};
 
 a(\"value\", \"value2\", \"value3\");
 
@@ -42,7 +43,8 @@ a(
 
 a(\'value\', \'value2\', a(\'long-nested-value\', \'long-nested-value2\', \'long-nested-value3\'));
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-const a = (param1, param2, param3) => {};
+const a = (param1, param2, param3) => {
+};
 
 a(\"value\", \"value2\", \"value3\");