Return an error object on connection failure

Fixes #9.

index.js

@@ -61,7 +61,9 @@ module.exports = function (url, opts, cb) {
 
 			if (res.statusCode < 200 || res.statusCode > 299) {
 				res.destroy();
-				cb(res.statusCode);
+				var err = new Error('Couldn\'t connect to ' + url + '.');
+				err.code = res.statusCode;
+				cb(err);
 				return;
 			}
 

test.js

@@ -28,9 +28,9 @@ it('should do HTTPS request', function (done) {
 	});
 });
 
-it('should should return status code as error when not 200', function (done) {
+it('should should return status code as error code when not 200', function (done) {
 	got('http://sindresorhus.com/sfsadfasdfadsga', function (err, data) {
-		assert.strictEqual(err, 404);
+		assert.strictEqual(err.code, 404);
 		done();
 	});
 });
@@ -84,7 +84,7 @@ it('should proxy errors to the stream', function (done) {
 	var stream = got('http://sindresorhus.com/sfsadfasdfadsga');
 
 	stream.on('error', function (error) {
-		assert.strictEqual(error, 404);
+		assert.strictEqual(error.code, 404);
 		done();
 	});
 });