Merge pull request bndr#185 from xiemaisi/patch-1

Fix likely typo of exclusive-or for exponentiation

artifact.go

@@ -107,7 +107,7 @@ func (a Artifact) getMD5local(path string) string {
  if err != nil {
  return ""
  }
- buffer := make([]byte, 2^20)
+ buffer := make([]byte, 1<<20)
  n, err := localFile.Read(buffer)
  defer localFile.Close()
  for err == nil {