Fix issues in tcell renderer and Windows build

- Fix display of CJK wide characters
- Fix horizontal offset of header lines
- Add support for keys with ALT modifier, shift-tab, page-up and down
- Fix util.ExecCommand to properly parse command-line arguments
- Fix redraw on resize
- Implement Pause/Resume for execute action
- Remove runtime check of GOOS
- Change exit status to 2 when tcell failed to start
- TBD: Travis CI build for tcell renderer
    - Pending. tcell cannot reliably ingest keys from tmux send-keys

src/util/util_windows.go

@@ -5,6 +5,8 @@ package util
 import (
 	"os"
 	"os/exec"
+
+	"github.com/junegunn/go-shellwords"
 )
 
 // ExecCommand executes the given command with $SHELL
@@ -13,5 +15,14 @@ func ExecCommand(command string) *exec.Cmd {
 	if len(shell) == 0 {
 		shell = "cmd"
 	}
-	return exec.Command(shell, "/c", command)
+	args, _ := shellwords.Parse(command)
+	allArgs := make([]string, len(args)+1)
+	allArgs[0] = "/c"
+	copy(allArgs[1:], args)
+	return exec.Command(shell, allArgs...)
+}
+
+// IsWindows returns true on Windows
+func IsWindows() bool {
+	return true
 }