Added ption to start basho bench as part of a node by calling basho_bench:main/1 not just as a standalone node from command line, the default option is the original standalone
FAIL_MSG behaviour to depend on included/standalone mode

If basho_bench is running standalone, call halt(1) on fatal errors
like before.  When included in another node, kill supervisor for a
more graceful exit.
Don't crash if basho_bench is already loaded
Merge github.com/esl/basho_bench master