add twitterStrategy

lib/crowi/index.js

@@ -266,6 +266,7 @@ Crowi.prototype.setupPassport = function() {
     this.passportService.setupLdapStrategy();
     this.passportService.setupGoogleStrategy();
     this.passportService.setupGitHubStrategy();
+    this.passportService.setupTwitterStrategy(); 
   }
   catch (err) {
     logger.error(err);