update travis

* use new Travis infrastructure
* specify Go versions (1.4.3, 1.5.1, tip)
* bypass the makefile to really build with all versions

.travis.yml

@@ -1,4 +1,13 @@
+sudo: false
+
 language: go
+go:
+  - 1.4.3
+  - 1.5.1
+  - tip
+
+install:
+  - go get -d
 
 script:
- - make test
+  - go test -v ./...