symfony:assets:update_version executed before composer

if composer install or update runs scripts (i.e. install:assets), it generates cache (precisely, compiles the container) and the newly set asset version is not taken into account.
Merge pull request #473 from gedsed/patch-1

symfony:assets:update_version executed before composer
Prepare 2.5.0 release
Bump version to 2.5.1.dev
removed unneeded dump of autoload files