Fix method "getTotalTime" to "getDuration".

See http://symfony.com/doc/current/cookbook/testing/profiling.html and http://api.symfony.com/2.3/Symfony/Component/HttpKernel/DataCollector/TimeDataCollector.html#method_getDuration
Merge pull request #352 from gnutix/patch-2

Fix method "getTotalTime" to "getDuration".