chore(package): update systemjs to version 6.2.4

Closes #64

Author: greenkeeper[bot]

package.json

@@ -107,7 +107,7 @@
     "rollup-plugin-sourcemaps": "^0.4.1",
     "rollup-plugin-uglify": "^2.0.1",
     "rxjs": "^5.0.1",
-    "systemjs": "^0.20.12",
+    "systemjs": "^6.2.4",
     "tslint": "^5.4.2",
     "tslint-jasmine-rules": "^1.3.0",
     "typescript": "^2.3.4",