vendor: add missing deps and remove go get in .travis.yml

Signed-off-by: Akihiro Suda <suda.akihiro@lab.ntt.co.jp>

vendor/github.com/stretchr/testify/require/doc.go

@@ -1,28 +0,0 @@
-// Package require implements the same assertions as the `assert` package but
-// stops test execution when a test fails.
-//
-// Example Usage
-//
-// The following is a complete example using require in a standard test function:
-//    import (
-//      "testing"
-//      "github.com/stretchr/testify/require"
-//    )
-//
-//    func TestSomething(t *testing.T) {
-//
-//      var a string = "Hello"
-//      var b string = "Hello"
-//
-//      require.Equal(t, a, b, "The two words should be the same.")
-//
-//    }
-//
-// Assertions
-//
-// The `require` package have same global functions as in the `assert` package,
-// but instead of returning a boolean result they call `t.FailNow()`.
-//
-// Every assertion function also takes an optional string message as the final argument,
-// allowing custom error messages to be appended to the message the assertion method outputs.
-package require