docs(LICENSE): update copyright year to 2018
docs(LICENSE): update copyright year to 2018

Closes #2113

Foxandxss/ng-bootstrap,benouat/ng-bootstrap,maxokorokov/core,maxokorokov/core,benouat/ng-bootstrap,ng-bootstrap/ng-bootstrap,benouat/ng-bootstrap,ng-bootstrap/core,jnizet/ng-bootstrap,ng-bootstrap/core,jnizet/ng-bootstrap,fbasso/ng-bootstrap,Foxandxss/ng-bootstrap,maxokorokov/core,ktriek/ng-bootstrap,pkozlowski-opensource/core,ng-bootstrap/ng-bootstrap,fbasso/ng-bootstrap,benouat/ng-bootstrap,maxokorokov/core,Foxandxss/ng-bootstrap,pkozlowski-opensource/core,fbasso/ng-bootstrap,ktriek/ng-bootstrap,fbasso/ng-bootstrap,ktriek/ng-bootstrap,ng-bootstrap/ng-bootstrap,ng-bootstrap/core,ktriek/ng-bootstrap,jnizet/ng-bootstrap,ng-bootstrap/ng-bootstrap,jnizet/ng-bootstrap,pkozlowski-opensource/core