Added 'grunt-svg-sprite' plugin

The plugin replaces 'svgmin' and 'svgstore' with an all-in-one and highly flexible solution for managing SVG assets.

Changes:
- Deleted 'assets/images/sprite/', SVG images can live anywhere within the source image directory;
- When compiled to 'www/assets/images/sprite.svg', the plugin generates an HTML file in 'assets/images/sprite.symbol.html' that serves as an index of the spritesheet's contents;
- A separator ("--") is used when traversing a directory structure for the symbol ID (e.g, 'sprite.svg#icons--social--twitter');

package.json

@@ -24,8 +24,7 @@
     "grunt-phplint": "0.0.0",
     "grunt-postcss": "0.0.0",
     "grunt-sass": "0.0.0",
-    "grunt-svgmin": "0.0.0",
-    "grunt-svgstore": "0.0.0",
+    "grunt-svg-sprite": "0.0.0",
     "load-grunt-config": "0.0.0",
     "postcss-banner": "0.0.0",
     "svg4everybody": "0.0.0"