chore(package): update shower-core to version 2.0.4
chore(package): update shower-core to version 2.0.4

http://greenkeeper.io/
belbiy/eugene-intro,Robsteranium/grafting-linked-data-slides,AnalogJ/capsulecd-slides,belbiy/eugene-intro,CaraWang/2016-talk-cnyes-elasticsearch,easy-deep-learning/event-emitter,rakchaev/offline_frontend-mix2016,CaraWang/2016-talk-cnyes-elasticsearch,rakchaev/assembly-pyatnica2016,Robsteranium/grafting-linked-data-slides,rakchaev/assembly-pyatnica2016,AnalogJ/capsulecd-slides,zolotyh/spa-pres,easy-deep-learning/event-emitter,rakchaev/offline_frontend-mix2016,zolotyh/spa-pres