fix: fix bug related to merging coverage reports see #482

Author: Benjamin Coe

package.json

@@ -82,7 +82,7 @@
     "find-up": "^1.1.2",
     "foreground-child": "^1.5.3",
     "glob": "^7.0.6",
-    "istanbul-lib-coverage": "^1.0.0",
+    "istanbul-lib-coverage": "^1.0.1",
     "istanbul-lib-hook": "^1.0.0",
     "istanbul-lib-instrument": "^1.4.2",
     "istanbul-lib-report": "^1.0.0-alpha.3",