Method renaming

I'd really like to see method renaming across files. Say i have following

``` ruby
def foo arg1, arg2
    args = arg1 + arg2
    puts "bar #{args}"
end
```

and

``` ruby
foobar.foo 'foo', 'bar'
```

in some other file, then i could rename the method foo into bar and all occurences of that method get refractored.
