Bring back coverage report. (#1620)

* Add back solidity-coverage (using fork).

* Pin fork version.

.travis.yml

@@ -25,11 +25,10 @@ jobs:
       name: "Unit tests"
       script: npm run test
 
-# solidity-coverage fails at parsing 0.5.x code
-#    - stage: tests
-#      name: "Unit tests with coverage report"
-#      script: npm run test
-#      env: SOLIDITY_COVERAGE=true
+    - stage: tests
+      name: "Unit tests with coverage report"
+      script: npm run test
+      env: SOLIDITY_COVERAGE=true
 
     - stage: tests
       name: "Unit tests using solc nightly"

package.json

@@ -55,7 +55,7 @@
     "openzeppelin-test-helpers": "^0.1.1",
     "pify": "^4.0.1",
     "solhint": "^1.5.0",
-    "solidity-coverage": "^0.5.4",
+    "solidity-coverage": "https://github.com:rotcivegaf/solidity-coverage.git#5875f5b7bc74d447f3312c9c0e9fc7814b482477",
     "truffle": "^5.0.0"
   },
   "dependencies": {}