Bump travis to 1.8 and 1.x.

.travis.yml

diff --git a/.travis.yml b/.travis.yml
index b130aaa..1174a9f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -6,8 +6,8 @@
 language: go
 
 go:
-- 1.2
-- 1.4.2
+- 1.8
+- 1.x
 
 before_install:
   - go get github.com/maruel/pre-commit-go/cmd/pcg