* Cache signature_help_trigger_chars
* Move code to the part which updating init_results.
* Tweaking delay for signature help
* Disable warning of unused-variables
* Improve signature help with lexima.vim
* Fix buffer change problem
* Display signature help after cursor jumped
* Fix event
* Add _ prefix for inner functions
* Highlight active parameter in signatureHelp
* Support `[number, number]` form of parameter label.
* Support parameter's documentation.
* Fix extracting parameter label