Ability to hook into dependencies for `default` or `index` task

[egeriis]

It would be great to have the ability to specify other tasks, that the default or index tasks depends on. It could simply be an array of custom gulp tasks specified in the Pho config:

var flatten = require('gulp-flatten');

require('pho-devstack')(gulp, {
    dependencies: ['fonts']
});

gulp.task('fonts', function() {
    gulp.src('src/bower_components/**/fonts/*')
        .pipe(flatten())
        .pipe(gulp.dest('dist/fonts'));
});

[PavelGavlik]

Great idea and it will be quite easy to implement.

[egeriis]

I'd be happy to do a pull request? Do you prefer it to be for index or default task?

[PavelGavlik]

For index task, it will work for incremental builds as well.