Add murmurhash3 as possible hash

Close #6.

lib/visitors/Hash.js

@@ -35,10 +35,18 @@ Hash.prototype.onAfterOutputFileBuild = function (packaging, outputFile) {
 };
 
 Hash.prototype._computeHash = function (filePath) {
-    var hash = crypto.createHash(this.hash);
     var content = grunt.file.read(filePath, {
         encoding : null
     });
+
+    if (this.hash == "murmur3") {
+        content = content.toString();
+        var digest = require('murmurhash-js').murmur3(content);
+        // murmur3 output is 32bit integer, convert it to base36 string (max. 7 chars from [0-9a-z])
+        return digest.toString(36);
+    }
+
+    var hash = crypto.createHash(this.hash);
     hash.update(content);
     return hash.digest('hex');
 };

package.json

@@ -10,6 +10,7 @@
   },
   "main": "lib/main.js",
   "dependencies": {
+    "murmurhash-js": "0.0.1",
     "uglify-js": "2.4.13"
   },
   "devDependencies": {