Added optional two-factor authentication

Gemfile.lock

@@ -43,6 +43,8 @@ GEM
       public_suffix (~> 2.0, >= 2.0.2)
     arel (7.1.4)
     ast (2.3.0)
+    attr_encrypted (3.0.3)
+      encryptor (~> 3.0.0)
     autoprefixer-rails (6.5.0.2)
       execjs
     av (0.9.0)
@@ -76,6 +78,7 @@ GEM
     bullet (5.3.0)
       activesupport (>= 3.0.0)
       uniform_notifier (~> 1.10.0)
+    chunky_png (1.3.8)
     climate_control (0.1.0)
     cocaine (0.5.8)
       climate_control (>= 0.0.3, < 1.0)
@@ -99,6 +102,12 @@ GEM
       railties (>= 4.1.0, < 5.1)
       responders
       warden (~> 1.2.3)
+    devise-two-factor (3.0.0)
+      activesupport
+      attr_encrypted (>= 1.3, < 4, != 2)
+      devise (~> 4.0)
+      railties
+      rotp (~> 2.0)
     diff-lcs (1.2.5)
     docile (1.1.5)
     domain_name (0.5.20161129)
@@ -113,6 +122,7 @@ GEM
       json
       thread
       thread_safe
+    encryptor (3.0.0)
     erubis (2.7.0)
     execjs (2.7.0)
     fabrication (2.15.2)
@@ -304,6 +314,9 @@ GEM
       redis (>= 2.2)
     responders (2.3.0)
       railties (>= 4.2.0, < 5.1)
+    rotp (2.1.2)
+    rqrcode (0.10.1)
+      chunky_png (~> 1.0)
     rspec (3.5.0)
       rspec-core (~> 3.5.0)
       rspec-expectations (~> 3.5.0)
@@ -416,6 +429,7 @@ DEPENDENCIES
   bullet
   coffee-rails (~> 4.1.0)
   devise
+  devise-two-factor
   doorkeeper
   dotenv-rails
   fabrication
@@ -455,6 +469,7 @@ DEPENDENCIES
   react-rails
   redis (~> 3.2)
   redis-rails
+  rqrcode
   rspec-rails
   rspec-sidekiq
   rubocop