Allow composer to use http

Fixes this:
>  - Installing pear-pear.horde.org/horde_translation (2.2.1)
>
>    Downloading: Connecting...    Downloading: Connecting...    Downloading: Connecting...
>
>                                                                               
>
>  [Composer\Downloader\TransportException]                                     
>
>  Your configuration does not allow connection to http://pear.horde.org. See   
>
>  https://getcomposer.org/doc/06-config.md#secure-http for details.            


https://travis-ci.org/owncloud/mail/jobs/111795408