Updated Travis CI configuration.

- Move to more recent version of Go, setting aside 1.1. - Use `install` instead of `before_script` to install library dependencies, as per [documentation](http://docs.travis-ci.com/user/languages/go/).

.travis.yml

diff --git a/.travis.yml b/.travis.yml
index 2efbc54..2c5ec79 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,7 +1,8 @@
 language: go
 go:
-  - 1.1
   - 1.2
+  - 1.3
   - tip
-before_script:
+install:
   - go get github.com/stretchr/testify
+  - go get github.com/stvp/go-udp-testing