Manage bower dependencies with grunt-bowercopy

Tracked bower dependencies are located at "src/sizzle" and "test/libs".
The source-destination mapping is in the Gruntfile.

When updating a bower dependency, update the version in bower.json, run
`grunt bower`, and then commit the result. When adding a dependency,
update the bowercopy task accordingly.

Fixes #14615.
Closes gh-1452.

Conflicts:
	bower.json
	test/index.html

package.json

@@ -32,7 +32,7 @@
   "devDependencies": {
     "archiver": "~0.4.10",
     "grunt": "~0.4.1",
-    "grunt-bower-task": "~0.3.2",
+    "grunt-bowercopy": "~0.4.1",
     "grunt-cli": "~0.1.11",
     "grunt-compare-size": "~0.4.0",
     "grunt-contrib-jshint": "~0.7.0",
@@ -49,9 +49,6 @@
   },
   "scripts": {
     "build": "npm install && grunt",
-
-    "install": "grunt bower",
-
     "start": "grunt watch",
     "test": "grunt"
   }