Add more spacing to #password_generator_toggle

Added slightly more left margin to the #password_generator_toggle link.

**Before:**
![add_new_user__inregister__wordpress](https://cloud.githubusercontent.com/assets/1231306/3599360/d704d8de-0ced-11e4-94a8-7c29143f67d6.png)

It's particularly close if the generator button has a focus state:
![add_new_user__inregister__wordpress](https://cloud.githubusercontent.com/assets/1231306/3599369/eef775c8-0ced-11e4-8359-65c3aab35079.png)

**After:**
![add_new_user__inregister__wordpress](https://cloud.githubusercontent.com/assets/1231306/3599355/c1a2b88a-0ced-11e4-8263-b42d54d1abd2.png)