Updated composer_options for the upcoming changes in composer.

Hi guys,

According to the [Composer Changelog](https://github.com/composer/composer/blob/1.0.0-alpha7/CHANGELOG.md), install and update commands will install dev dependencies by default at the next alpha release so I updated the composer_options to use the new --no-dev option.

I'm sorry for the whitespaces changes, my editor automatically trim them on save. If you want the diff without the whitespaces changes, please add `?w=1` on the PR url.

Of course, I'll update the docs asap.

Regards.