Path to cmd.exe

This line:

https://github.com/tadzik/Shell-Command/blob/1145ea0ff71507b2fe932fca6d2a68d4004c7d12/lib/Shell/Command.pm#L7

Assumes that cmd.exe is on the PATH. This is not guaranteed on a Windows
system, so it might be helpful to change to the full path:

C:\Windows\System32\cmd.exe

or to emit some warning if not found. The current incarnation just fails
silently with regard to a missing cmd.exe.

[lizmat]

Is this still an issue?