Do not put spaces on empty for loop (#169)

```js
for (;;) {
```

instead of

```js
for (; ; ) {
```

src/printer.js

@@ -874,7 +874,15 @@ function genericPrintNoParens(path, options, print) {
 
     return group(concat(parts));
   case "ForStatement":
-    // TODO Get the for (;;) case right.
+    const body = adjustClause(path.call(print, "body"), options);
+
+    if (!n.init && !n.test && !n.update) {
+      return concat([
+        'for (;;)',
+        body,
+      ]);
+    }
+
     return concat([
       "for (",
       group(
@@ -896,7 +904,7 @@ function genericPrintNoParens(path, options, print) {
         ])
       ),
       ")",
-      adjustClause(path.call(print, "body"), options)
+      body,
     ]);
   case "WhileStatement":
     return concat([

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

@@ -280,3 +280,12 @@ function corge(x: boolean) {
 }
 "
 `;
+
+exports[`test for.js 1`] = `
+"for (;;) {}
+for (var i = 0; i < 10; ++i) {}
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+for (;;) {}
+for (var i = 0; i < 10; ++i) {}
+"
+`;

tests/for/for.js

@@ -0,0 +1,2 @@
+for (;;) {}
+for (var i = 0; i < 10; ++i) {}