chore: explicit upgrade of istanbul-reports (#816)

Author: bcoe

package.json

@@ -88,7 +88,7 @@
     "istanbul-lib-instrument": "^1.10.0",
     "istanbul-lib-report": "^1.1.3",
     "istanbul-lib-source-maps": "^1.2.3",
-    "istanbul-reports": "^1.1.4",
+    "istanbul-reports": "^1.4.0",
     "md5-hex": "^1.2.0",
     "merge-source-map": "^1.0.2",
     "micromatch": "^2.3.11",