Hystrix open threshold documentation (#2136)
Hystrix open threshold documentation (#2136)

fixes gh-1943
joshiste/spring-cloud-netflix,ryanjbaxter/spring-cloud-netflix,bijukunjummen/spring-cloud-netflix,ryanjbaxter/spring-cloud-netflix,joshiste/spring-cloud-netflix,brenuart/spring-cloud-netflix,sfat/spring-cloud-netflix,bijukunjummen/spring-cloud-netflix,ryanjbaxter/spring-cloud-netflix,bijukunjummen/spring-cloud-netflix,brenuart/spring-cloud-netflix,shuiky/spring-cloud-netflix,brenuart/spring-cloud-netflix,joshiste/spring-cloud-netflix,shuiky/spring-cloud-netflix,joshiste/spring-cloud-netflix,sfat/spring-cloud-netflix,bijukunjummen/spring-cloud-netflix,spring-cloud/spring-cloud-netflix,sfat/spring-cloud-netflix,bijukunjummen/spring-cloud-netflix,ryanjbaxter/spring-cloud-netflix,joshiste/spring-cloud-netflix,brenuart/spring-cloud-netflix,shuiky/spring-cloud-netflix,sfat/spring-cloud-netflix,spring-cloud/spring-cloud-netflix,shuiky/spring-cloud-netflix,sfat/spring-cloud-netflix,brenuart/spring-cloud-netflix,shuiky/spring-cloud-netflix,ryanjbaxter/spring-cloud-netflix