gruntjs/grunt — pull request #511 by rxaviers (2012-11-06 17:59:41+00:00)
Title: Properly write error/failure log to stderr

Usually, an application outputs its messages to `stdin`, but errors to `stderr`. So, it gets easier to filter its messages out by piping the streams like the below.

```
$ grunt mytask > normal 2> errors
```

Currently, all `grunt.log.fn` functions write to `stdin` (including `grunt.log.error` and `grunt.log.fail`). This patch simply make the following change:

* log.ok -> stdin
* log.error -> stderr*
* log.success -> stdin
* log.fail -> stderr*