Delete vendored code and update CI to Go 1.13 (#158)

As the Go community transitions to using the modules ecosystem,
we want to only support one way of managing dependencies.
So this change moves to only using Go modules for dependency management.

This means that our effective minimum Go version increases to Go 1.11.
To account for this, we also update:
  - the documentation
  - Makefile
  - CI scripts

1 files changed, 0 insertions, 22 deletions

diff --git a/vendor/golang.org/x/sys/windows/str.go b/vendor/golang.org/x/sys/windows/str.go
deleted file mode 100644
index 917cc2a..0000000
--- a/vendor/golang.org/x/sys/windows/str.go
+++ /dev/null
@@ -1,22 +0,0 @@
-// Copyright 2009 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// +build windows
-
-package windows
-
-func itoa(val int) string { // do it here rather than with fmt to avoid dependency
-	if val < 0 {
-		return "-" + itoa(-val)
-	}
-	var buf [32]byte // big enough for int64
-	i := len(buf) - 1
-	for val >= 10 {
-		buf[i] = byte(val%10 + '0')
-		i--
-		val /= 10
-	}
-	buf[i] = byte(val + '0')
-	return string(buf[i:])
-}