Add support for input from pipe

Usage: env | pt PATH

However, it does not support the following features:
* Detect the encoding from the input pipe.
* Input stream, such as tail -f
Add test for input from pipe
Fixed for cygwin

In non-standard terminal such as mintty and cygwin, because it detects the pipe
incorrectly, also check named pipe.
Revert "Fixed for cygwin"

This reverts commit 0cadc56e4657561caf79e2b64d513edfaa63723d.
Merge branch 'master' into patch/input_pipe

Conflicts:
	search/option/option.go
Merge pull request #22 from shiena/patch/input_pipe

Add support for input from pipe