correct island hero heading and gutter width

https://bugzilla.mozilla.org/show_bug.cgi?id=951164

Reviews

![reviews](https://f.cloud.github.com/assets/211578/1765425/b3e5a378-6735-11e3-935c-7f5d9a16f823.png)

Also aligned the heading with form elements (the "Log In" text was 12px off before)

![log-in](https://f.cloud.github.com/assets/211578/1765427/b5dfb24a-6735-11e3-8c48-db0d4b144d9c.png)