chore(package): update rxjs-marbles to version 4.2.0

Closes #9

Author: greenkeeper[bot]

package.json

@@ -116,7 +116,7 @@
     "rollup-plugin-sourcemaps": "^0.4.2",
     "rollup-plugin-typescript2": "^0.12.0",
     "rxjs": "^5.5.6",
-    "rxjs-marbles": "^2.3.1",
+    "rxjs-marbles": "^4.2.0",
     "semantic-release": "^15.0.0",
     "ts-jest": "^22.0.0",
     "ts-node": "^5.0.1",