When the slave metrics request takes more than 10 seconds the response
to the /metrics endpoint ends up being discarded by Prometheus which
defaults to a timeout of 10 seconds. Fix by ignoring slaves that take
longer than 8 seconds to respond to the metrics request.
Use lib* prefix for the modules impored from the lib package to help
distinguish them more from ordinary variables. Fix up the naming
convention for files to be consistently lowercase_underscore for
JavaScript files.
Split up codebase into the packages @clsterio/lib, @clusterio/master,
@clusterio/slave, and @clusterio/ctl using lerna to manage them. This
will allow deployment to use only the parts needed reducing install
size, and better separate the code into shared library, master, slave
and control.