Update to latest sbroker

[fishcakez]

!!WORK IN PROGRESS!!

• Support pool resizing via an sregulator
• Support short circuiting requests via sprotector (on by default)
• Set SASL :alarm_handler alarms when appropriate (on by default, though overload alarm off if using protector)

Need to test defaults, certainly I think :idle_target might be wrong, perhaps 5%-10% of :idle_interval is better. If :idle_target is a higher proportion of :idle_interval it will cause the pool to grow quicker and drop slower.

Also I haven't added the ability to load balance brokers.

sbroker master requires OTP 18(/Elixir 1.2), it was costing an unreasonable about of code (500loc) to support a version that wouldn't work well (fallback to :erlang.now/0 for time)

[josevalim]

:heart: :green_heart: :blue_heart: :yellow_heart: :purple_heart:

sbroker master requires OTP 18(/Elixir 1.2), it was costing an unreasonable about of code (500loc) to support a version that wouldn't work well (fallback to :erlang.now/0 for time)

:tada: