update submodule urls to public urls

Some submodule urls were of the form
git@github.com:owner/example.git
which requires a public key to download.
Converting these to the public url format
https://github.com/owner/example.git allows them
to update without requiring the public key
Merge pull request #3 from salcode/submod-update-url

update submodule urls to public urls to make it easier for those that don't have a Github public key to set up the project.