`grunt.file` documents unreleased feature: grunt.file.copy options "process"

Originally report: [Issue # 1440](https://github.com/gruntjs/grunt/issues/1440) (gruntjs/grunt)

[**`grunt.file.md`**](https://github.com/gruntjs/grunt-docs/blob/master/grunt.file.md#gruntfilecopy) advises that for the `grunt.file.copy` function:

``` js
// The source file contents, source file path, and destination file path
// are passed into this function, whose return value will be used as the
// destination file's contents. If this function returns `false`, the file
// copy will be aborted.
process: processFunction,
```

In particular: _"The ... **destination file path** [is] passed into this function"_

As of the latest release of Grunt, [0.4.5](https://github.com/gruntjs/grunt/releases/tag/v0.4.5), this is not true. The documentation needs to be corrected to remove this, or advise that it will be available in future releases.