Return null for external URLs that contain querystrings

Photon doesn't support them.

Closes #4.

Squashed commit of the following:

commit 7a5e4049d05e865b9daa280df80369b8219a0c77
Author: Ben Lowery <ben.lowery@automattic.com>
Date:   Mon Feb 1 10:42:36 2016 -0500

    Return null for external URLs that contain querystrings

commit b7fd525f82d19a8208d2ff7e293c7fccebcd7b12
Author: Ben Lowery <ben.lowery@automattic.com>
Date:   Wed Apr 15 14:28:59 2015 -0400

    Don't attempt to photon URLs that use a querystring.

    Photon doesn't support them.

packages/photon.js/index.js

@@ -59,6 +59,10 @@ function photon (imageUrl, opts) {
     params.pathname = parsedUrl.pathname;
     params.hostname = parsedUrl.hostname;
   } else {
+    // Photon does not support URLs with a querystring component
+    if (parsedUrl.search) {
+      return null;
+    }
     params.pathname = url.format( parsedUrl ).substring(1);
     params.hostname = serverFromPathname( params.pathname );
   }
@@ -108,4 +112,3 @@ function serverFromPathname( pathname ) {
   debug('determined server "%s" to use with "%s"', server, pathname);
   return server + '.wp.com';
 }
-

packages/photon.js/test/test.js

@@ -44,13 +44,13 @@ describe('photon()', function () {
     var alternateUrl = 'https://i1.wp.com/www.gravatar.com/avatar/693307b4e0cb9366f34862c9dfacd7fc';
 
     assertHostedOnPhoton(photonedUrl);
-    assert.notStrictEqual(alternateUrl, photonedUrl);
-    assert.strictEqual(alternateUrl, photon(alternateUrl));
+    assert.notStrictEqual(photonedUrl, alternateUrl);
+    assert.strictEqual(photon(alternateUrl), alternateUrl);
   });
 
   it('should handle photoning a photoned url', function() {
     var url = photon('http://example.com/image.png');
-    assert.strictEqual(url, photon(url));
+    assert.strictEqual(photon(url), url);
   });
 
   it('should add width parameters if specified', function() {
@@ -60,10 +60,10 @@ describe('photon()', function () {
     assertQuery(photonedUrl, { 'w':'50' });
   });
 
-  it('should encode query args for non-photon hosts', function() {
-    var photonedUrl = photon('http://example.com/image.png?foo=bar');
+  it('should return null for URLs with querystrings from non-photon hosts', function() {
+    var url = 'http://example.com/image.png?foo=bar';
 
-    assertPathname(photonedUrl, '/example.com/image.png%3Ffoo=bar');
+    assert.strictEqual(photon(url), null);
   });
 
   it('should handle protocolless URLs', function() {