Issue #75: Fix 'unsupported fd type: TTY' error in pty.open()

Applying the fix described in issue #32 for a similar issue, which
replaces "new net.Socket()" with "new tty.ReadStream()"

Signed-off-by: Dan O'Donovan <dan@emutex.com>
Merge pull request #76 from Dan-Emutex/master

Issue #75: Fix 'unsupported fd type: TTY' error in pty.open()