Feature: puppet-load - a tool to stress-test master compilation

This commit introduce a new executable (ext/puppet-load) which aims
to simulate concurrent clients to stress-test load a puppet master.
At the end of a run, it produces some statistics.

This tool is very lightweight:

• it runs under Event Machine (and thus is event-driven)
• it doesn't do anything with the received catalog

This tool, to run, needs access to:

• a certificate/private_key pair from a node known by the master
• a fact file like those persisted on the master
• obviously a puppet-master running somewhere

Refer to the embedded help for options and run examples.

TODO:

• fetch different nodes catalog
• exercise the file server

Signed-off-by: Brice Figureau <brice-puppet@daysofwonder.com>