chore(package): update sass-loader to version 7.3.0

Closes #40

Author: greenkeeper[bot]

package.json

@@ -97,7 +97,7 @@
     "rollup-plugin-uglify": "3.0.0",
     "run-sequence": "2.2.1",
     "rxjs": "^6.3.3",
-    "sass-loader": "7.1.0",
+    "sass-loader": "7.3.0",
     "schematics-utilities": "^1.1.2",
     "source-map-loader": "0.2.4",
     "to-string-loader": "1.1.5",