Playing with OmniAuth

However OmniAuth is mainly used for authorization. So let's try a more
lightweight approach with just OpenID.

Gemfile.lock

@@ -183,8 +183,6 @@ GEM
     omniauth-amazon (1.0.1)
       omniauth (~> 1.0)
       omniauth-oauth2 (~> 1.1)
-    omniauth-facebook (4.0.0)
-      omniauth-oauth2 (~> 1.2)
     omniauth-github (1.2.3)
       omniauth (~> 1.5)
       omniauth-oauth2 (>= 1.4.0, < 2.0)
@@ -199,9 +197,9 @@ GEM
     omniauth-oauth2 (1.4.0)
       oauth2 (~> 1.0)
       omniauth (~> 1.2)
-    omniauth-twitter (1.4.0)
-      omniauth-oauth (~> 1.1)
-      rack
+    omniauth-openid (1.0.1)
+      omniauth (~> 1.0)
+      rack-openid (~> 1.3.1)
     orm_adapter (0.5.0)
     paperclip (5.1.0)
       activemodel (>= 4.2.0)
@@ -220,6 +218,9 @@ GEM
       slop (~> 3.4)
     puma (3.8.2)
     rack (2.0.1)
+    rack-openid (1.3.1)
+      rack (>= 1.1.0)
+      ruby-openid (>= 2.1.8)
     rack-test (0.6.3)
       rack (>= 1.0)
     rails (5.0.2)
@@ -259,6 +260,7 @@ GEM
     responders (2.3.0)
       railties (>= 4.2.0, < 5.1)
     ruby-graphviz (1.2.3)
+    ruby-openid (2.7.0)
     ruby-progressbar (1.8.1)
     sass (3.4.23)
     sass-rails (5.0.6)
@@ -284,7 +286,7 @@ GEM
     spring-watcher-listen (2.0.1)
       listen (>= 2.7, < 4.0)
       spring (>= 1.2, < 3.0)
-    sprockets (3.6.3)
+    sprockets (3.7.1)
       concurrent-ruby (~> 1.0)
       rack (> 1, < 3)
     sprockets-es6 (0.9.2)
@@ -344,11 +346,10 @@ DEPENDENCIES
   minitest-reporters
   omniauth
   omniauth-amazon
-  omniauth-facebook
   omniauth-github
   omniauth-google-oauth2
   omniauth-launchpad!
-  omniauth-twitter
+  omniauth-openid
   paperclip
   pg
   pg_search
@@ -360,7 +361,7 @@ DEPENDENCIES
   slim-rails
   spring
   spring-watcher-listen (~> 2.0.0)
-  sprockets (= 3.6.3)
+  sprockets
   therubyracer
   turbolinks (~> 5)
   uglifier (>= 1.3.0)