Fixes in the threading Guide
Fixes in the threading Guide

ozydingo/byebug,saisai/byebug,deivid-rodriguez/byebug,yui-knk/byebug,icebreaker/byebug,ozydingo/byebug,yui-knk/byebug,deivid-rodriguez/byebug,guilherme/byebug,guilherme/byebug,miamiruby/byebug,icebreaker/byebug,yui-knk/byebug,k0kubun/byebug,saisai/byebug,scalp42/byebug,webdev1001/byebug,miamiruby/byebug,k0kubun/byebug,webdev1001/byebug,guilherme/byebug,scalp42/byebug,os97673/byebug,k0kubun/byebug,deivid-rodriguez/byebug,os97673/byebug