Add .rustfmt to unify styling

[3Hren]

The only problem I discovered is line breaking. I really hate when rustfmt does the following change:

pub fn long_function<T, E>(&mut self, arg1: Arg1, arg2: Arg2, arg3: T) -> Result<T, E>
where
    T: Display,
    E: Error
{
   unimplemented!()
}

pub fn long_function<T, E>(&mut self, 
                           arg1: Arg1, 
                           arg2: Arg2, 
                           arg3: T) 
    -> Result<T, E>
where
    T: Display,
    E: Error
{
   unimplemented!()
}