Upgrade solidity-parser to 0.18.0 (#829)

Author: cgewecke

package.json

@@ -25,7 +25,7 @@
   "license": "ISC",
   "dependencies": {
     "@ethersproject/abi": "^5.0.9",
-    "@solidity-parser/parser": "^0.16.0",
+    "@solidity-parser/parser": "^0.18.0",
     "chalk": "^2.4.2",
     "death": "^1.1.0",
     "detect-port": "^1.3.0",