vendor: only vendor on emitted binaries

Moves the vendor/ directory to cmd/vendor. Vendored binaries are built
from cmd/, which is backed by symlinks pointing back to repo root.

cmd/vendor/github.com/codegangsta/cli/cli.go

@@ -0,0 +1,40 @@
+// Package cli provides a minimal framework for creating and organizing command line
+// Go applications. cli is designed to be easy to understand and write, the most simple
+// cli application can be written as follows:
+//   func main() {
+//     cli.NewApp().Run(os.Args)
+//   }
+//
+// Of course this application does not do much, so let's make this an actual application:
+//   func main() {
+//     app := cli.NewApp()
+//     app.Name = "greet"
+//     app.Usage = "say a greeting"
+//     app.Action = func(c *cli.Context) {
+//       println("Greetings")
+//     }
+//
+//     app.Run(os.Args)
+//   }
+package cli
+
+import (
+	"strings"
+)
+
+type MultiError struct {
+	Errors []error
+}
+
+func NewMultiError(err ...error) MultiError {
+	return MultiError{Errors: err}
+}
+
+func (m MultiError) Error() string {
+	errs := make([]string, len(m.Errors))
+	for i, err := range m.Errors {
+		errs[i] = err.Error()
+	}
+
+	return strings.Join(errs, "\n")
+}