Should pg_tools submodule dependency be over https?

In the submodule config:
```
[submodule "schemas/pg_tools"]
path = schemas/pg_tools
url = git@github.com:jonkeane/pg_tools.git
```

We connect over SSH. In contexts where SSH credentials are unavailable, or complicated to include (for instance, Travis), this fails. Since pg_tools is a public repository, the SSH connection is unnecessary. Should we change it to the https URL?

Start with the submodule configuration shown in the issue and inspect how the schemas/pg_tools dependency is fetched in environments without SSH credentials. Change the public repository URL to HTTPS, then verify that the submodule can be initialized without SSH access and that the Travis context no longer fails.

Written by the indexing model from the issue text.