fix(polyline): icon to icons
fix(polyline): icon to icons

Changes the typename from 'Icon' to 'Icons' according to the Google API.

fixes #948
SebastianM/angular2-google-maps,SebastianM/angular2-google-maps,SebastianM/angular2-google-maps,SebastianM/angular-google-maps,SebastianM/angular-google-maps