Added docblocks to FileNotFoundException
Added docblocks to FileNotFoundException

Amrit01/flysystem,dshafik/flysystem,hannesvdvreken/flysystem,concrete5/flysystem,barryvdh/flysystem,rossriley/flysystem,sachintaware/flysystem,nao-pon/flysystem,mhlavac/flysystem,oswaldderiemaecker/flysystem,mhlavac/flysystem,sohelrana820/flysystem,CarsonF/flysystem,mapyo/flysystem,twistor/flysystem,dstockto/flysystem,farmisen/flysystem,twistor/flysystem