Move to vendored dependencies (#86)

* Add vendored dependencies
* Update README install instructions

Author: sideshow

README.md

@@ -17,17 +17,15 @@ APNS/2 is a go package designed for simple, flexible and fast Apple Push Notific
 ## Install
 
 - Make sure you have [Go](https://golang.org/doc/install) installed and have set your [GOPATH](https://golang.org/doc/code.html#GOPATH).
-- Download and install the dependencies:
+- Install apns2:
 
 ```sh
-go get -u golang.org/x/net/http2
-go get -u golang.org/x/crypto/pkcs12
+go get -u github.com/sideshow/apns2
 ```
 
-- Install apns2:
-
+If you are running the test suite you will also need to install testify:
 ```sh
-go get -u github.com/sideshow/apns2
+go get -u github.com/stretchr/testify
 ```
 
 ## Example