Pass HTTPS client parameters.

For more detailed control over HTTPS client behaviour, pass through the
parameters listed here:
http://nodejs.org/api/https.html#https_https_request_options_callback

The `rejectUnauthorized` parameter is omitted, because it overlaps with
the existing `secure` parameter:
https://github.com/nodejitsu/node-http-proxy/blob/master/README.md#using-https

Conflicts:
	test/lib-http-proxy-common-test.js

lib/http-proxy/common.js

@@ -34,7 +34,8 @@ common.setupOutgoing = function(outgoing, options, req, forward) {
   outgoing.port = options[forward || 'target'].port ||
                   (isSSL.test(options[forward || 'target'].protocol) ? 443 : 80);
 
-  ['host', 'hostname', 'socketPath'].forEach(
+  ['host', 'hostname', 'socketPath', 'pfx', 'key',
+    'passphrase', 'cert', 'ca', 'ciphers', 'secureProtocol'].forEach(
     function(e) { outgoing[e] = options[forward || 'target'][e]; }
   );
 

test/lib-http-proxy-common-test.js

@@ -250,6 +250,7 @@ describe('lib/http-proxy/common.js', function () {
 
         expect(outgoing.headers.host).to.eql('mycouch.com:6984');
       });
+
       it('should correctly set the port to the host when it is a non-standard port when setting host and port manually (which ignores port)', function () {
         var outgoing = {};
         common.setupOutgoing(outgoing, {
@@ -264,6 +265,38 @@ describe('lib/http-proxy/common.js', function () {
       })
     });
 
+    it('should pass through https client parameters', function () {
+      var outgoing = {};
+      common.setupOutgoing(outgoing,
+      {
+        agent     : '?',
+        target: {
+          host      : 'how',
+          hostname  : 'are',
+          socketPath: 'you',
+          protocol: 'https:',
+          pfx: 'my-pfx',
+          key: 'my-key',
+          passphrase: 'my-passphrase',
+          cert: 'my-cert',
+          ca: 'my-ca',
+          ciphers: 'my-ciphers',
+          secureProtocol: 'my-secure-protocol'
+        }
+      },
+      {
+        method    : 'i',
+        url      : 'am'
+      });
+
+      expect(outgoing.pfx).eql('my-pfx');
+      expect(outgoing.key).eql('my-key');
+      expect(outgoing.passphrase).eql('my-passphrase');
+      expect(outgoing.cert).eql('my-cert');
+      expect(outgoing.ca).eql('my-ca');
+      expect(outgoing.ciphers).eql('my-ciphers');
+      expect(outgoing.secureProtocol).eql('my-secure-protocol');
+    });
   });
 
   describe('#setupSocket', function () {