Fix compatibility with omniauth-oauth 1.4+ and allow http locally (#4)

* Fix compatibility with omniauth-oauth 1.4+

References:
* omniauth/omniauth-oauth2#70
* omniauth/omniauth-oauth2@2615267
* omniauth/omniauth-oauth2#82
* jdennes/omniauth-createsend#3
* WebTheoryLLC/omniauth-twitch#4
* jdennes/omniauth-createsend#5
* DripEmail/omniauth-drip#6

* Don't force https if it's localhost

* Allow 127.0.0.1 and localhost to be on http

* Lookup IP for the given host and force ssl

Avoid to force ssl for local IPs (127/8 network)

* Improve resolving

* Improve even more

* Fix regexp

* Allow fe80::* entirely

lib/omniauth/strategies/infusionsoft.rb

@@ -1,4 +1,5 @@
 require 'omniauth-oauth2'
+require 'resolv'
 
 module OmniAuth
   module Strategies
@@ -22,11 +23,15 @@ def full_host
             uri.path = ''
             uri.query = nil
             #infusionsoft requires https for callback urls
-            uri.scheme = 'https'
+            #force ssl for all hosts except: 127.x.x.x, fe80:: and ::1
+            uri.scheme = 'https' unless Resolv.getaddress(uri.host) =~ /^(fe80::|127|::1)/
             uri.to_s
         end
       end
 
+      def callback_url
+        full_host + script_name + callback_path
+      end
     end
   end
 end