Fix accidental fall-through in Flow type parsing. (#82)

When parsing a primary type, `>` would erroneously be treated like `(`.

src/plugins/flow.js

@@ -506,6 +506,7 @@ pp.flowParsePrimaryType = function () {
 
         return this.finishNode(node, "FunctionTypeAnnotation");
       }
+      break;
 
     case tt.parenL:
       this.next();