Added Dutch translation (#72)

Author: freenerd

instructions.js

@@ -1,6 +1,7 @@
 var instructionsDe = require('./instructions/de.json');
 var instructionsEn = require('./instructions/en.json');
 var instructionsFr = require('./instructions/fr.json');
+var instructionsNl = require('./instructions/nl.json');
 
 module.exports = {
     get: function(language) {
@@ -11,6 +12,8 @@ module.exports = {
             return instructionsDe;
         case 'fr':
             return instructionsFr;
+        case 'nl':
+            return instructionsNl;
         default:
             throw 'invalid language ' + language;
         }