* use materialize() for highlight references
* re-enable highlight references by default
* unlet s:Dispose()
* fix checking for isUndefined()
* update callbag to v0.3.0
* dispose if exists
* add callbag.vim
* add diagnostics
* add comments
* implement cancel
* optimize cancelled=1
* handle more cancel cases
* use callbag for echo.vim
* rename to _enable() _disable() and also check for changedtick
* move to internal
* group lsp#request
* ignore terminal for echo
* dont bother to subscribe if diagnostics echo not enabled
* remove deprecation comment
* update callbag.vim to v0.1.0
* fix lint issues