v0.4.0: Add exec.Sudo(h) exec option (#29)

API changes:

Sudo

Before:

h.Exec("sudo ps")

Now:

h.Exec("ps", exec.Sudo(h))

Upload

Before:

h.Upload(src, dst) // always used sudo to overwrite destination

After:

h.Upload(src, dst, exec.Sudo(h)) // now requires exec.Sudo(h) to overwrite non-user files