add a path wrapper for Windows

Signed-off-by: Jeff Carr <jcarr@wit.com>

windowsWrapper.go

@@ -1,10 +1,19 @@
 package shell
 
 import "runtime"
+import "strings"
 
 func Execname(filename string) string {
-	if runtime.GOOS == "windows" {
-		return filename + ".exe"
+	if runtime.GOOS != "windows" {
+		return filename
 	}
+	return Path(filename) + ".exe"
+}
+
+func Path(filename string) string {
+	if runtime.GOOS != "windows" {
+		return filename
+	}
+	filename = strings.Replace(filename, "/", "\\", -1)
 	return filename
 }