...until we decide to switch to ES2015+
This is a breaking change for users that may rely on `assets/bpmn-font` being present in the library. BREAKING CHANGE: * use `bpmn-font` package, specifically `bpmn-font/dist` if you need the font previously contained in the assets directory.
* replace grunt with npm scripts * copy static assets to dist directory * build and copy library variants to dist directory Related to #725