Update composer.json

Updated the required version of symfony/property-access so that it will play nice with the latest Silex which uses 2.4.1.
Update PagerfantaServiceProvider.php

Added support for Twitter Bootstrap 3, as supported by Pagerfanta.
Update PagerfantaServiceProvider.php

Corrected the indentation.
Update PagerfantaServiceProvider.php

Added comma at the end.
Merge pull request #5 from jjsee/master

Updated Silex support + added Pagerfanta Twitter Bootstrap 3 View support