Drop support for go 1.7 because of echo

Echo dropped the support for go 1.7 which leads us
to either drop support for echo, or go 1.7. :/

Author: sharpner

.travis.yml

@@ -1,10 +1,10 @@
 language: go
 
 go:
-  - 1.7
-  - 1.8
-  - 1.9
-  - tip
+  - "1.8"
+  - "1.9"
+  - "1.10"
+  - "tip"
 
 sudo: false