add stylelint npm package

.stylelintrc.json

@@ -0,0 +1,124 @@
+{
+  "rules": {
+    "at-rule-empty-line-before": [ "always", {
+      "except": [ "blockless-group", "first-nested" ],
+      "ignore": ["after-comment"]
+    }],
+    "at-rule-name-case": "lower",
+    "at-rule-name-space-after": "always-single-line",
+    "at-rule-semicolon-newline-after": "always",
+    "block-closing-brace-newline-after": "always",
+    "block-closing-brace-newline-before": "always",
+    "block-no-empty": true,
+    "block-opening-brace-newline-after": "always",
+    "block-opening-brace-space-before": "always",
+    "color-hex-case": "lower",
+    "color-hex-length": "short",
+    "color-no-invalid-hex": true,
+    "declaration-bang-space-after": "never",
+    "declaration-bang-space-before": "always",
+    "declaration-block-no-ignored-properties": true,
+    "declaration-block-no-shorthand-property-overrides": true,
+    "declaration-block-properties-order": [[
+    {
+      "order": "flexible",
+      "properties": [
+        "position",
+        "z-index",
+        "top",
+        "right",
+        "bottom",
+        "left"
+      ]},
+    {
+      "order": "flexible",
+      "properties": [
+        "height",
+        "max-height",
+        "min-height",
+        "width",
+        "max-width",
+        "min-width",
+        "display",
+        "box-sizing",
+        "overflow",
+        "overflow-x",
+        "overflow-y",
+        "padding",
+        "padding-top",
+        "padding-right",
+        "padding-bottom",
+        "padding-left",
+        "border",
+        "border-top",
+        "border-right",
+        "border-bottom",
+        "border-left",
+        "border-radius",
+        "margin",
+        "margin-top",
+        "margin-right",
+        "margin-bottom",
+        "margin-left"
+      ]}], { "unspecified": "bottom" }],
+    "declaration-block-semicolon-newline-after": "always",
+    "declaration-block-semicolon-space-before": "never",
+    "declaration-block-single-line-max-declarations": 1,
+    "declaration-block-trailing-semicolon": "always",
+    "declaration-colon-newline-after": "always-multi-line",
+    "declaration-colon-space-before": "never",
+    "function-calc-no-unspaced-operator": true,
+    "function-comma-newline-after": "never-multi-line",
+    "function-comma-space-after": "always",
+    "function-comma-space-before": "never",
+    "function-linear-gradient-no-nonstandard-direction": true,
+    "function-max-empty-lines": 0,
+    "function-name-case": "lower",
+    "function-parentheses-newline-inside": "never-multi-line",
+    "function-parentheses-space-inside": "never",
+    "function-whitespace-after": "always",
+    "indentation": 2,
+    "max-empty-lines": 1,
+    "media-feature-colon-space-after": "always",
+    "media-feature-colon-space-before": "never",
+    "media-feature-no-missing-punctuation": true,
+    "media-feature-range-operator-space-after": "always",
+    "media-feature-range-operator-space-before": "always",
+    "media-query-list-comma-newline-after": "always-multi-line",
+    "media-query-list-comma-space-after": "always-single-line",
+    "media-query-list-comma-space-before": "never",
+    "media-query-parentheses-space-inside": "never",
+    "no-eol-whitespace": true,
+    "no-extra-semicolons": true,
+    "no-invalid-double-slash-comments": true,
+    "no-missing-eof-newline": true,
+    "number-leading-zero": "always",
+    "number-no-trailing-zeros": true,
+    "number-zero-length-no-unit": true,
+    "property-case": "lower",
+    "rule-non-nested-empty-line-before": [ "always-multi-line", {
+      "ignore": ["after-comment"]
+    } ],
+    "selector-attribute-brackets-space-inside": "never",
+    "selector-attribute-operator-space-after": "never",
+    "selector-attribute-operator-space-before": "never",
+    "selector-combinator-space-after": "always",
+    "selector-combinator-space-before": "always",
+    "selector-list-comma-newline-after": "always",
+    "selector-list-comma-space-before": "never",
+    "selector-max-empty-lines": 0,
+    "selector-pseudo-class-case": "lower",
+    "selector-pseudo-class-parentheses-space-inside": "never",
+    "selector-pseudo-element-case": "lower",
+    "selector-pseudo-element-colon-notation": "double",
+    "selector-pseudo-element-no-unknown": true,
+    "selector-type-case": "lower",
+    "shorthand-property-no-redundant-values": true,
+    "string-no-newline": true,
+    "unit-case": "lower",
+    "unit-no-unknown": true,
+    "value-list-comma-newline-after": "always-multi-line",
+    "value-list-comma-space-after": "always-single-line",
+    "value-list-comma-space-before": "never"
+  }
+}

package.json

@@ -9,11 +9,12 @@
   "dependencies": {},
   "devDependencies": {
     "eslint-plugin-mozilla": "0.0.3",
-    "eslint": "2.9.0"
+    "eslint": "2.9.0",
+    "stylelint":"6.3.3"
   },
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1",
-    "eslint": "eslint . --ext=js,jsm && eslint vertical-tabbrowser.xml"
+    "lint": "eslint . --ext=js,jsm vertical-tabbrowser.xml && stylelint \"**/*.css\""
   },
   "repository": {
     "type": "git",