fix(package): update solidity-coverage to version 0.7.3

Closes #200

Author: greenkeeper[bot]

package.json

@@ -91,7 +91,7 @@
     "request": "^2.85.0",
     "resolve": "1.8.1",
     "sendgrid": "^5.2.3",
-    "solidity-coverage": "^0.5.2",
+    "solidity-coverage": "^0.7.3",
     "solium": "^1.1.7",
     "source-map-loader": "^0.2.3",
     "strip-ansi": "4.0.0",