chore: remove commitmsg linting

Since all contributions are handled via PR (squash merge), there is no reason to enforce contributors to use the convention in their working branch.

package.json

@@ -32,7 +32,6 @@
     "documentation": "gitdown ./.README/README.md --output-file ./README.md; npm run documentation-add-assertions",
     "create-index": "create-index ./src --update-index",
     "precommit": "npm run lint && npm run test && npm run format-json",
-    "commitmsg": "conventional-changelog-lint -e",
     "format-json": "jsonlint --sort-keys --in-place --indent '  ' ./src/configs/recommended.json && echo '' >> ./src/configs/recommended.json"
   },
   "devDependencies": {
@@ -43,7 +42,6 @@
     "babel-preset-stage-0": "^6.5.0",
     "babel-register": "^6.14.0",
     "chai": "^3.5.0",
-    "conventional-changelog-lint": "^1.0.1",
     "create-index": "^0.1.3",
     "eslint": "^3.16.0",
     "eslint-config-canonical": "1.8.1",