chore(package): update rollup-plugin-sourcemaps to version 0.6.1

Closes #92

Author: greenkeeper[bot]

package.json

@@ -95,7 +95,7 @@
     "rollup": "^0.66.6",
     "rollup-plugin-commonjs": "^9.2.1",
     "rollup-plugin-node-resolve": "^3.4.0",
-    "rollup-plugin-sourcemaps": "0.4.2",
+    "rollup-plugin-sourcemaps": "0.6.1",
     "rollup-plugin-uglify": "3.0.0",
     "run-sequence": "2.2.1",
     "rxjs": "^6.4.0",