Add stylelinting to ensure mapboxgl- prefix on all classes (#4584)

* Add stylelint CLI and Add mapbox class name rule in stylelintrc

* # This is a combination of 3 commits.
# This is the 1st commit message:
Stylelint works for application

# This is the commit message #2:

WIP modify lint-css script in package.json

# This is the commit message #3:

Ammend warning for lint-css npm script

* Stylelint implemented for application

WIP modify lint-css script in package.json

Ammend warning for lint-css npm script

Add csscolorparser

* Add lintx to script file

* Took out lintx

* Took out lintx

* Resolve comments to 4584 PR

* Resolve PR comments

* Ignore stylelint in .flowconfig and remove true from scripts

.flowconfig

@@ -2,6 +2,7 @@
 
 .*/node_modules/jsonlint/.*
 .*/node_modules/jsonlint-lines-primitives/.*
+.*node_modules.*/stylelint.*
 .*/node_modules/unflowify/.*
 .*/test/unit/style-spec/fixture/invalidjson.input.json
 

.stylelintrc

@@ -0,0 +1,5 @@
+{
+  "rules": {
+    "selector-class-pattern": "mapboxgl-[a-z-]+"
+  }
+}

package.json

@@ -71,6 +71,7 @@
     "request": "^2.79.0",
     "sinon": "^2.1.0",
     "st": "^1.2.0",
+    "stylelint": "^7.10.1",
     "tap": "^10.3.0",
     "vinyl": "^2.0.1",
     "vinyl-fs": "^2.4.4",
@@ -115,8 +116,9 @@
     "start-docs": "npm run build-min && npm run build-docs && jekyll serve --watch",
     "lint": "eslint --cache --ignore-path .gitignore src test bench docs/_posts/examples/*.html debug/*.html",
     "lint-docs": "documentation lint src/index.js",
+    "lint-css": "stylelint 'dist/mapbox-gl.css'",
     "open-changed-examples": "git diff --name-only mb-pages HEAD -- docs/_posts/examples/*.html | awk '{print \"http://127.0.0.1:4000/mapbox-gl-js/example/\" substr($0,33,length($0)-37)}' | xargs open",
-    "test": "run-s lint test-unit test-flow",
+    "test": "run-s lint lint-css test-unit test-flow",
     "test-suite": "run-s test-render test-query",
     "test-suite-clean": "find test/integration/*-tests -mindepth 2 -type d  -not \\( -exec test -e \"{}/style.json\" \\; \\) -print | xargs -t rm -r",
     "test-unit": "tap --reporter dot --no-coverage test/unit",