Add example script for recording MySQL slave stats.

Most of these aren't particularly interesting.  The ones I'm interested
in are `slave_{io,sql}_running` and `seconds_behind_master`.

I`m not sure if we want to use the same namespace here (`mysql`) as in
the normal `mysql-stats.sh` script.
Merge mysql-slave-status (#4) into master

Add example script for recording MySQL slave stats.

Most of these aren't particularly interesting.  The ones I'm interested
in are `slave_{io,sql}_running` and `seconds_behind_master`.

I'm not sure if we want to use the same namespace here (`mysql`) as in
the normal `mysql-stats.sh` script.