chore(package): update coveralls to version 2.11.15
chore(package): update coveralls to version 2.11.15

https://greenkeeper.io/
mseemann/angular2-mdl,mseemann/angular2-mdl,c1rno/angelhack_frontend_prototype,c1rno/angelhack_frontend_prototype,c1rno/angelhack_frontend_prototype,mseemann/angular2-mdl,c1rno/angelhack_frontend_prototype,mseemann/angular2-mdl