Added terminal detection

tty/Terminal_darwin.go

@@ -0,0 +1,6 @@
+package tty
+
+// IsTerminal returns true if the file descriptor is a terminal.
+func IsTerminal(fd uintptr) bool {
+	return false
+}

tty/Terminal_linux.go

@@ -0,0 +1,9 @@
+package tty
+
+import "golang.org/x/sys/unix"
+
+// IsTerminal returns true if the file descriptor is a terminal.
+func IsTerminal(fd uintptr) bool {
+	_, err := unix.IoctlGetTermios(int(fd), unix.TCGETS)
+	return err == nil
+}

tty/Terminal_windows.go

@@ -0,0 +1,6 @@
+package tty
+
+// IsTerminal returns true if the file descriptor is a terminal.
+func IsTerminal(fd uintptr) bool {
+	return false
+}