Make application_name pg client init param configurable

[mecampbellsoup]

Allows client conns to specify a value for application_name instead of just hard-coding to "pgmoon", e.g.:

    pg_settings = {
        host = ip,
        port = '5432',
        database = os.getenv('POSTGRES_DATABASE'),
        user = os.getenv('POSTGRES_USERNAME'),
        password = os.getenv('POSTGRES_PASSWORD'),
        application_name = 'api-gateway'  -- previously this was hardcoded to "pgmoon"
    }

@leafo I should just be able to run make build to generate the *.lua files correct?

Resolves #107.

[leafo]

@mecampbellsoup That's correct, make build will generate lua files from the corresponding moon files. We should check in all generated lua files so luarocks can install the module without any compile step or additional dependencies.