Finish first pass at and docment Bootstrap v2-ish theme

* Adds new "theme" example
* Adds new theme.less file to provide all the overrides and additional
styles for the theme
* theme.less compiles, via Grunt, to two new files to `dist/css`,
bootstrap-theme.css and bootstrap-theme.min.css

Gruntfile.js

@@ -83,6 +83,17 @@ module.exports = function(grunt) {
         },
         src: ['less/bootstrap.less'],
         dest: 'dist/css/<%= pkg.name %>.min.css'
+      },
+      theme: {
+        src: ['less/theme.less'],
+        dest: 'dist/css/<%= pkg.name %>-theme.css'
+      },
+      theme_min: {
+        options: {
+          compress: true
+        },
+        src: ['less/theme.less'],
+        dest: 'dist/css/<%= pkg.name %>-theme.min.css'
       }
     },