Update .travis.yml

Adds go 1.7

.travis.yml

diff --git a/.travis.yml b/.travis.yml
index 5c7621e..f56caed 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,11 +3,15 @@
 install: 
   - go get github.com/stretchr/testify/assert
 
-go:
-  - 1.1
-  - 1.2
-  - 1.3
-  - 1.4
-  - 1.5
-  - 1.6
-  - tip
+matrix:
+  include:
+    - go: 1.1
+    - go: 1.2
+    - go: 1.3
+    - go: 1.4
+    - go: 1.5
+    - go: 1.6
+    - go: 1.7
+    - go: tip
+  allow_failures:
+    - go: tip