Fix default port numbers for Net::HTTP adapters

When Addressable::URI is used, the `port` property will be nil unless
port was explicitly specified. This made Addressable unusable in HTTPS
scenarios with Net::HTTP adapters, which would default to port 80 even
when the scheme was "https".

lib/faraday/adapter/net_http.rb

@@ -92,7 +92,7 @@ module Faraday
           Net::HTTP::Proxy(proxy[:uri].host, proxy[:uri].port, proxy[:user], proxy[:password])
         else
           Net::HTTP
-        end.new(env[:url].host, env[:url].port)
+        end.new(env[:url].host, env[:url].port || (env[:url].scheme == 'https' ? 443 : 80))
       end
 
       def configure_ssl(http, ssl)

test/adapters/net_http_test.rb

@@ -1,4 +1,6 @@
 require File.expand_path('../integration', __FILE__)
+require 'ostruct'
+require 'uri'
 
 module Adapters
   class NetHttpTest < Faraday::TestCase
@@ -10,5 +12,34 @@ module Adapters
 
     Integration.apply(self, *behaviors)
 
+    def test_no_explicit_http_port_number
+      url = URI('http://example.com')
+      url.port = nil
+
+      adapter = Faraday::Adapter::NetHttp.new
+      http = adapter.net_http_connection(:url => url, :request => {})
+
+      assert_equal 80, http.port
+    end
+
+    def test_no_explicit_https_port_number
+      url = URI('https://example.com')
+      url.port = nil
+
+      adapter = Faraday::Adapter::NetHttp.new
+      http = adapter.net_http_connection(:url => url, :request => {})
+
+      assert_equal 443, http.port
+    end
+
+    def test_explicit_port_number
+      url = URI('https://example.com:1234')
+
+      adapter = Faraday::Adapter::NetHttp.new
+      http = adapter.net_http_connection(:url => url, :request => {})
+
+      assert_equal 1234, http.port
+    end
+
   end
 end