Add french translation (#69)

Author: guillaumerose

instructions.js

@@ -1,5 +1,6 @@
 var instructionsDe = require('./instructions/de.json');
 var instructionsEn = require('./instructions/en.json');
+var instructionsFr = require('./instructions/fr.json');
 
 module.exports = {
     get: function(language) {
@@ -8,6 +9,8 @@ module.exports = {
             return instructionsEn;
         case 'de':
             return instructionsDe;
+        case 'fr':
+            return instructionsFr;
         default:
             throw 'invalid language ' + language;
         }