Added polyfill changes to the changelog.
Added polyfill changes to the changelog.

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