switch from internal Throttle to guava's RateLimiter. #229
as we bumped from guava 11 to 14, had to resolve the SystemUtils's use of
removed guava methods (already fixed in master)
Merge branch '229' into 1.1
rev number
Merge pull request #231 from jasobrown/1.1

switch from internal Throttle to guava's RateLimiter. #229

reviewed by @timiblossom