Send buffer visit / unload events to completer server
Send buffer visit / unload events to completer server

The TypeScript completion service requires BufferVisit and
BufferUnload events to provide semantic results, so we add
support for them in this patch.

abingham/emacs-ycmd,abingham/emacs-ycmd,ptrv/emacs-ycmd,abingham/emacs-ycmd,emacsmirror/ycmd,emacsmirror/ycmd,abingham/emacs-ycmd,ptrv/emacs-ycmd,ptrv/emacs-ycmd,ptrv/emacs-ycmd,phst/emacs-ycmd,phst/emacs-ycmd,emacsmirror/ycmd,phst/emacs-ycmd,ptrv/emacs-ycmd,emacsmirror/ycmd,emacsmirror/ycmd,phst/emacs-ycmd,emacsmirror/ycmd,phst/emacs-ycmd,phst/emacs-ycmd,ptrv/emacs-ycmd,abingham/emacs-ycmd,abingham/emacs-ycmd