Add coverage command

package.json

@@ -4,7 +4,8 @@
   "description": "Easily enable fast Ajax navigation on any website (using pushState +  xhr)",
   "main": "src/pjax.js",
   "scripts": {
-    "test": "testling"
+    "test": "testling",
+    "coverage": "browserify -t coverify tests/**/*.js | testling | coverify"
   },
   "repository": {
     "type": "git",
@@ -26,8 +27,10 @@
   },
   "homepage": "https://github.com/MoOx/pjax",
   "devDependencies": {
+    "browserify": "^3.46.0",
     "connect": "^2.14.4",
     "connect-livereload": "^0.3.2",
+    "coverify": "^1.0.6",
     "gulp": "^3.5.6",
     "gulp-autoprefixer": "0.0.7",
     "gulp-browserify": "^0.5.0",
@@ -46,6 +49,7 @@
     "rework-vars": "^2.0.0",
     "rimraf": "^2.2.6",
     "tape": "^2.12.3",
+    "testling": "^1.6.1",
     "uglifyify": "^2.1.1"
   },
   "testling": {