add autoprefixer

Gruntfile.js

 module.exports = function (grunt) {
+  grunt.loadNpmTasks('grunt-autoprefixer');
   grunt.loadNpmTasks('grunt-contrib-less');
   grunt.loadNpmTasks('grunt-contrib-concat');
   grunt.loadNpmTasks('grunt-contrib-connect');
   grunt.loadNpmTasks('grunt-contrib-clean');
   grunt.loadNpmTasks('grunt-contrib-watch');
 
+  var configBridge = grunt.file.readJSON('./bower_components/bootstrap/grunt/configBridge.json', { encoding: 'utf8' });
+
   // Project configuration.
   grunt.initConfig({
     pkg: grunt.file.readJSON('package.json'),
@@ -46,6 +49,14 @@ module.exports = function (grunt) {
         files: {}
       }
     },
+    autoprefixer: {
+      options: {
+        browsers: configBridge.config.autoprefixerBrowsers
+      },
+      dist: {
+        src: ['*/bootstrap.css', '*/bootstra.min.css']
+      }
+    },
     watch: {
       files: ['*/variables.less', '*/bootswatch.less', '*/index.html'],
       tasks: 'build',
@@ -103,10 +114,15 @@ module.exports = function (grunt) {
     grunt.config('less.dist.files', files);
     grunt.config('less.dist.options.compress', false);
 
-    grunt.task.run(['concat', 'less:dist', 'clean:build',
+    grunt.task.run(['concat', 'less:dist', 'prefix:' + lessDest, 'clean:build',
       compress ? 'compress:'+lessDest+':'+'<%=builddir%>/' + theme + '/bootstrap.min.css':'none']);
   });
 
+  grunt.registerTask('prefix', 'autoprefix a generic css', function(fileSrc) {
+    grunt.config('autoprefixer.dist.src', fileSrc);
+    grunt.task.run('autoprefixer');
+  });
+
   grunt.registerTask('compress', 'compress a generic css', function(fileSrc, fileDst) {
     var files = {}; files[fileDst] = fileSrc;
     grunt.log.writeln('compressing file ' + fileSrc);

package.json

@@ -15,6 +15,7 @@
   "devDependencies": {
     "bower": "~1.2.8",
     "grunt": "~0.4.2",
+    "grunt-autoprefixer": "~1.0.1",
     "grunt-contrib-clean": "~0.5.0",
     "grunt-contrib-concat": "~0.3.0",
     "grunt-contrib-connect": "~0.8.0",