Remove node-inspector

* make node-inspector a dev dependency

This PR removes the `node-inspector` optional dependency and converts it into a dev-dependency so that it no longer gets installed when _swagger-js_ is added to a project (npm installs optional deps by default unless --no-optional is used).

* remove node-inspector dependency altogether

Author: fgnass

package.json

@@ -19,7 +19,6 @@
     "build-bundle": "NODE_ENV=production webpack -p --config ./webpack.bundle.config.js",
     "watch": "webpack --config webpack.config.js --watch --progress",
     "test": "NODE_ENV=test node --debug ./node_modules/.bin/_mocha --recursive --compilers js:babel-core/register",
-    "inspector": "node-debug",
     "test:watch": "npm run test -- -w",
     "lint": "eslint src/ test/",
     "deps-license": "license-checker --production --csv --out $npm_package_config_deps_check_dir/licenses.csv && license-checker --development --csv --out $npm_package_config_deps_check_dir/licenses-dev.csv",
@@ -58,9 +57,6 @@
     "webpack-bundle-size-analyzer": "^2.2.0",
     "xmock": "^0.3.0"
   },
-  "optionalDependencies": {
-    "node-inspector": "0.12.8"
-  },
   "dependencies": {
     "babel-runtime": "^6.23.0",
     "btoa": "1.1.2",