expected support for linux idioms such as grep and yes

[sstarcher]

What operating system and terminal are you using? osx, iterm2

An example that showcases the bug.

• Create a prompt and run it on the command line.
• go run . | grep 12.11
• yes | go run .

What did you expect to see?

• I would expect to still see the prompt.
• I would also expect the prompt to respond to keypresses
• Expected support for piping yes into the command, but instead a yes/no prompt would consider it an error

[noerw]

see also #328

[mislav]

Duplicate of https://github.com/AlecAivazis/survey/issues/328.

Currently it's only possible to use Survey when both stdin and stdout are connected to a terminal.