Use 'rerequest' on facebook's auth to deal with users not sharing email

If the user tried to authenticate via Facebook and didn't share the email,
the login would fail and the user would have to sign in to Facebook and
remove the Mconf app to be able to try to login on Mconf again.

Now it will request users to share their email when they click in the
sign in button if they didn't share yet.

.env.development

@@ -33,12 +33,15 @@ MCONF_EMAIL_TRACK_CLICKED=true
 # MCONF_REDIS_PORT='6379'
 # MCONF_REDIS_DB='0'
 
-# Omniauth for google and facebook need API keys.
-# More instructions can be found on https://github.com/omniauth/omniauth/wiki/List-of-Strategies
-# Then add the following:
+# Omniauth authentication, more at https://github.com/omniauth/omniauth/wiki/List-of-Strategies
+# Get the keys for Google at https://console.developers.google.com
+# You must enable the "People API" and "Google+ API"
 # MCONF_OMNIAUTH_GOOGLE_KEY='yourgooglekey'
-# MCONF_OMNIAUTH_FACEBOOK_KEY='yourfacebookkey'
 # MCONF_OMNIAUTH_GOOGLE_SECRET='yourgooglesecret'
+# Get the keys for Facebook at
+# * http://developers.facebook.com/docs/authentication
+# * https://developers.facebook.com/apps
+# MCONF_OMNIAUTH_FACEBOOK_KEY='yourfacebookkey'
 # MCONF_OMNIAUTH_FACEBOOK_SECRET='yourfacebooksecret'
 
 # Flag to use authentication on playback url

config/initializers/devise.rb

@@ -224,7 +224,7 @@
   end
 
   if Rails.application.config.omniauth_facebook_key.present? && Rails.application.config.omniauth_facebook_secret.present?
-    config.omniauth :facebook, Rails.application.config.omniauth_facebook_key, Rails.application.config.omniauth_facebook_secret, {}
+    config.omniauth :facebook, Rails.application.config.omniauth_facebook_key, Rails.application.config.omniauth_facebook_secret, auth_type: 'rerequest'
   end
 
   # ==> Warden configuration