LC should recalculate hints after a document is externally edited

[mqudsi]

• Did you upgrade to latest plugin version? yes
• Did you upgrade to/compile latest binary? 0.1.154
• (Neovim users only) Did you check output of :checkhealth LanguageClient? yes
• Did you check [troubleshooting]? yes

Describe the bug

This is hopefully very straightforward:

After a document is externally modified (in this case, !cargo fmt) and hotreloaded, the syntax/compilation errors/hints are not correctly recalculated/redrawn and may be presented on the wrong lines.

I imagine all it needs is an additional autocmd BufWrite trigger.

Environment

• neovim/vim version (nvim --version or vim --version): v0.5.0-23-gafd576ee9
• This plugin version (git rev-parse --short HEAD): 4fd272b0dbf96d7a4fd5d9d840780638f514aa7c
• This plugin's binary version (bin/languageclient --version): 0.1.154
• Minimal vimrc content (A minimal vimrc is the smallest vimrc that could reproduce the issue. Refer to an example [here][min-vimrc.vim]): n/a (rust)
• Language server link and version: n/a (rust)

Here's a screenshot demonstrating the issue:

Perhaps more useful, here's a very brief screen capture of the issue: https://youtu.be/xbTYAqlycIA