Add a Makefile target for pulse tests

Add a Makefile target to run the pulse tests. The goal is to make it as simple
as possible to run these tests in order to increase the likelihood they are
run during the normal course of code reviews and not simply forgotten. The
pulse test modules are moved up directly into the test directory to allow
rebar to find them and the test module is renamed to bitcask_pulse for easier
identification.  Also a new version of rebar that can properly execute the new
Makefile target is added.