.travis.yml: replace service account key

Replace the old key with a new one, because the old one was
compromised.

Change-Id: If1095a4c44e65ea2a545660a5ba2c0779eb1ae02
Reviewed-on: https://code-review.googlesource.com/13131
Reviewed-by: Sarah Adams <shadams@google.com>
Reviewed-by: Chris Broadfoot <cbro@google.com>

.travis.yml

@@ -5,9 +5,10 @@ language: go
 go:
   - 1.6
   - 1.7
-
+  - 1.8
+
 before_install:
-  - openssl aes-256-cbc -K $encrypted_7fd28a0c5534_key -iv $encrypted_7fd28a0c5534_iv -in key.json.enc -out key.json -d
+  - openssl aes-256-cbc -K $encrypted_6c6ebd86ce52_key -iv $encrypted_6c6ebd86ce52_iv -in key.json.enc -out key.json -d
 
 install:
   - go get -v google.golang.org/api/...