Facilitate collecting data from stderr and stdout

The change collects output spat to stderr and stdout so it can be used by the callback / exit callback.

I recommend to keep the `callback` and `exitCallback` with same signature to be compatible with the usage-pattern of libs such as async.

Assume the following user code:

```
var path        = require('path')
  , async       = require('async')
  , log         = require('log4js').getLogger('zipper util')
  , controller  = Object.create(require('control').controller)
  , ssh         = controller.ssh
  , argv        = process.argv
  , tmpDir      = "/tmp/usr/zip/"
  , packName
  , packPath   
  , tmpZipDir
  , source
  ;

if (argv[0] == 'node') argv.shift(); //throw 'node'
argv.shift(); //throw the script name

controller.address = argv.shift()


packName = argv.shift();
if (!packName) throw new Error('package name must be provided');

tmpZipDir = path.join(tmpDir, packName);
packPath = path.join( tmpDir, packName ) + ".zip"

async.waterfall(
  [ function mkdir_tmp(done) {
        step = 'mkdir';
        log.debug('creating archive folder');
        ssh('mkdir -p ' + tmpZipDir, done, done);
    }
  , function copying(done) {
        step = 'copying';
        log.debug('copying files from ' + source);
        ssh('cp ' + source + ' ' + tmpZipDir , done, done);
    }
  , function archive(done) {
        step = 'archiving';
        log.debug('creating archive');
        ssh('zip -r " + packPath + " " + tmpZipDir + "/*', done, done);
    }
  , function store(done) {
        step = 'store on s3 through s3-fuse';
        log.debug('storing archive on fixture-storage');
        ssh('mv ' + packPath + " /mnt/s3/archives", done, done);
    }
  , function cleanup_db(done) {
        step = 'cleanup';
        log.debug('cleaning up temp');
        ssh("rm -f -r " + tmpZipDir , done, done);
    }
  ]
, function(err, std) {

      /***********************************************
        AND NOW - when something is wrong
           any communication passed in this failed step will be in 
           (in addition to err to be the exit-code)

        std.err //returns data gathered in stderr during the failed / last command
        std.out //returns data gathered in stdout during the failed / last command
       ***********************************************/

  }
)

```

basically, we're creating instrumentation that allows the programmer focus just on the commands he needs to use, so the example above is already pesudo code.

the end code looks better like:
```
task("magic", "do the magic", function(controller, source, tmpZipDir) {
    var packPath = path.join( tmpDir, packName ) + ".zip";

    require('./lib/scripter').run(controller
    , { 'creating archive folder' : "mkdir -p " + tmpZipDir
      , 'copying files'           : "cp " + source + " " + tmpZipDir 
      , 'creating archive'        : "zip -r " + packPath + " " + tmpZipDir + "/*"
      , 'storing on s3-fuse'      : "mv " + packPath + " /mnt/s3/archives"
      , 'cleanup'                 : "rm -f -r " + tmpZipDir
      }
    , function(errCode, step, std ) {
         //I hope you see where it's going ;)

      }
    )
});
```

the proposed change will utilize us a lot.
we need it for both production code, and obviously unit-tests...