Use os.MkdirAll instead of mkdir to crate a directory

This works on all platforms.

Signed-off-by: Asias He <asias@cloudius-systems.com>
repository: Make it work on Windows

Later we should create a helper to copy a file using native golang.

Signed-off-by: Asias He <asias@cloudius-systems.com>
Merge pull request #55 from asias/win

Win