Fix checkout of blue-penguin and add nikhil-theme correctly

 * `--recursive` checkout was broken because of blue-penguin url, `git submodule update --init` was not working either
 * Added `nikhil-theme` correctly, previously I had edited `.gitmodules` directly - did not realize that correct way to do it is `git submodule add <repo_path> <name>` - should this be documented in README ?