prettier 2

Summary:
Quick notes:

- This looks worse than it is. It adds mandatory parentheses to single argument lambdas. Lots of outrage on Twitter about it, personally I'm {emoji:1f937_200d_2642} about it.
- Space before function, e.g. `a = function ()` is now enforced. I like this because both were fine before.
- I added `eslint-config-prettier` to the config because otherwise a ton of rules conflict with eslint itself.

Close https://github.com/facebook/flipper/pull/915

Reviewed By: jknoxville

Differential Revision: D20594929

fbshipit-source-id: ca1c65376b90e009550dd6d1f4e0831d32cbff03

desktop/app/src/dispatcher/user.tsx

@@ -14,10 +14,10 @@ import {getUser, logoutUser} from '../fb-stubs/user';
 
 export default (store: Store, _logger: Logger) => {
   getUser()
-    .then(user => {
+    .then((user) => {
       store.dispatch(login(user));
     })
-    .catch(e => {
+    .catch((e) => {
       store.dispatch(logout());
       console.error(e);
     });