Add .aac files support

Tested with [a file](http://download.wavetlan.com/SVV/Media/HTTP/AAC/Roxio_Media_Manager/RoxioMediaManager_test4_AAC-LC_v4_Stereo_CBR_64kbps_44100Hz.aac) found on [wavetlan](http://download.wavetlan.com/SVV/Media/HTTP/http-aac.htm)