title: Add, Commit and Push at Once using GULP-GIT
body: <p>I'm trying to create a task that does <code>add .</code> , <code>commit</code>, and <code>push</code> in a single command line like : <code>gulp gitsend -m "My changes"</code></p>
  
  <pre><code>var gulp = require('gulp');
  var argv = require('yargs').argv;
  var git = require('gulp-git');
  
  gulp.task('gitsend', function() {
  if (argv.m) {
      console.log('adding, commiting and pushing to git...');
      return gulp.src('.')
      .pipe(git.add())
      .pipe(git.commit(argv.m)
      .pipe(git.push('origin', 'master', function (err) {
          if (err) throw err;
      })));
  }
  });
  </code></pre>
  
  <p>But this is not working: it throws an exception:</p>
  
  <pre><code>/Users/me/myproj/front/node_modules/gulp-git/node_modules/through2/node_modules/readable-stream/lib/_stream_readable.js:623
      var written = dest.write(chunk);
                         ^
  TypeError: undefined is not a function
      at write (/Users/me/myproj/front/node_modules/gulp-git/node_modules/through2/node_modules/readable-stream/lib/_stream_readable.js:623:24)
      at flow (/Users/me/myproj/front/node_modules/gulp-git/node_modules/through2/node_modules/readable-stream/lib/_stream_readable.js:632:7)
      at DestroyableTransform.pipeOnReadable (/Users/me/myproj/front/node_modules/gulp-git/node_modules/through2/node_modules/readable-stream/lib/_stream_readable.js:664:5)
      at DestroyableTransform.emit (events.js:104:17)
      at emitReadable_ (/Users/me/myproj/front/node_modules/gulp-git/node_modules/through2/node_modules/readable-stream/lib/_stream_readable.js:448:10)
      at emitReadable (/Users/me/myproj/front/node_modules/gulp-git/node_modules/through2/node_modules/readable-stream/lib/_stream_readable.js:444:5)
      at readableAddChunk (/Users/me/myproj/front/node_modules/gulp-git/node_modules/through2/node_modules/readable-stream/lib/_stream_readable.js:187:9)
      at DestroyableTransform.Readable.push (/Users/me/myproj/front/node_modules/gulp-git/node_modules/through2/node_modules/readable-stream/lib/_stream_readable.js:149:10)
      at DestroyableTransform.Transform.push (/Users/me/myproj/front/node_modules/gulp-git/node_modules/through2/node_modules/readable-stream/lib/_stream_transform.js:145:32)
      at Array.forEach (native)
  </code></pre>
  
  <p>Any idea what's wrong and how can I archive my need ?
  Thank you.</p>