perf(linters): Greatly improve the npm run lint task speed

The `npm run lint` task now takes about ~3s on my machine (was
taking XXX).

Previously:
```
$ time npm run lint
npm run lint  10,84s user 1,22s system 107% cpu 11,187 total
```
Now:
```
$ time npm run lint
npm run lint  3,73s user 0,28s system 116% cpu 3,445 total
```

Basically all I did was specify the `./**/*.js` or `./**/*.scss`
pattern on both linters and that makes it much faster.

For scss, I also cleaned up a bit the list of ignore patterns (as we
now use Jekyll 3, some files do not have the front-matter anymore and
so we do not need to exclude them).

.sass-lint.yml

@@ -1,14 +1,12 @@
 options:
   formatter: stylish
 files:
-  include: '**/*.scss'
+  include: 
+    '+(docs|src)/**/*.scss'
   ignore:
-    - 'node_modules/**/*'
-    - 'docs/examples/*/main.scss' # Jekyll files requiring front-matter
-    - 'docs/css/main.scss' # Jekyll files requiring front-matter
-    - 'docs/css/examples/*/main.scss' # Jekyll files requiring front-matter
-    - 'docs/css/bootstrap/**/*' # Vendor
+    - 'docs/css/bootstrap/**/*.scss' # Vendor
     - 'docs/css/_syntax-highlighting.scss' # Vendor
+    - 'docs/examples/**/main.scss' # Files with front-matter
     # Contains asset_path() call to jekyll-assets. sass-lint cannot disable rules inline
     # https://github.com/sasstools/sass-lint/issues/544
     - 'docs/css/_home.scss'

package.json

@@ -10,8 +10,8 @@
     "dev:docs": "./scripts/dev-docs.sh",
     "doctoc": "doctoc --maxlevel 3 README.md CONTRIBUTING.md",
     "lint": "npm run lint:js && npm run lint:css",
-    "lint:js": "eslint . --quiet --no-color",
-    "lint:css": "sass-lint --verbose",
+    "lint:js": "./scripts/lint-js",
+    "lint:css": "./scripts/lint-css",
     "docs:jsdoc": "babel-node ./scripts/docs/gen-widget-doc.js",
     "docs:update-website": "./scripts/docs/update-website.sh",
     "docs:update-website-search-index": "./scripts/docs/update-website-search-index.sh",

scripts/lint-css

@@ -0,0 +1,2 @@
+#!/usr/bin/env bash
+sass-lint --verbose

scripts/lint-js

@@ -0,0 +1,2 @@
+#!/usr/bin/env bash
+eslint ./*.js ./**/*.js --quiet