Renasme uv_isopen -> isopen
Add callback for write
Make writes task-blocking by default
Actually look for Scheduler in Base
Don't use blocking writes from the Scheduler
Fix build on Linux
Fix write return value for UTF8
Address Jeff's comments
Make async write close the stream on error
Merge pull request #3726 from JuliaLang/kf/syncwrite

Makes `write` Task-blocking by default