Expecting [secure] as output

This is useful if your database uses true/false for state and want to make prometheus alerts based on that.
Before, booleans were not able to be parsed.  See issue #201

We don't need GIT_API_KEY to clone the assets branch, so don't require it.

This functionality was added in c225a1e1
but not documented.

for memory parameters for bytes.

When you area monitoring server from cloud providers the exporter
IP/hostname is not the server IP, so add some constant labels is useful
on dashboards and alerts.

And is very important to use with `--disable-default-metrics` to add
info like `datname` and figure out the database name that you are
monitoring