Emit drain in compress middleware.
Emit drain in compress middleware.

Fixes #541.

qitianchan/connect,RickyDan/connect,khalerc/connect,keenwon/connect,behind2/connect,llwanghong/connect,chinazhaghai/connect,liuwei9413/connect,mi2oon/connect,gtomitsuka/connect,senchalabs/connect,mi2oon/connect,RoseTHERESA/connect,dkfiresky/connect,tanveer12332/connect,lian774739140/connect,khirayama/connect,austincitylimits/connect,davehorton/drachtio,wghust/connect