Prevent entryCreateUser from being used when forbidClientAccountCreation is enabled

Even when **forbidClientAccountCreation** was enabled users could still be added from the client if you manually went to the /sign-up route, or by calling **entryCreateUser** from the console:
```js
Meteor.call(
    'entryCreateUser',
    {email:'asdf@asdf.com',password:'asdfasdf1'},
    function(e){console.log(e);
});
```
This commit disables the **entryCreateUser** method when **forbidClientAccountCreation** is enabled.
In the code? It's not my doing. That's from the master branch: [signUp.coffee#L160](https://github.com/Differential/accounts-entry/blob/master/client/views/signUp/signUp.coffee#L160)

I just added a conditional at the top and added an indent to all these lines, that's why they're modified (If there's a way to prevent that I'd like to know!)