initial language server protocol implementation
Here is the initial implementation of some of the features of language server protocol (#26)
Currently it only supports 3 method - initialize, textDocument/didOpen, textDocument/documentSymbols as a proof of concept.
This vim plugin is not included in this CR (but if any one wants to try it out let me know and I can share it)

The implementation is similar to https://github.com/sourcegraph/go-langserver
My next step would be to add support for more of the lsp features and also write a vscode plugin so that I can test with a real client.
Note: I'm not a go dev so this may not be idiomatic go code but feel free to comment.
Coverage decreased (-2.4%) to 80.917% when pulling d320a462dc82a48dea0a5581e3e53f5a1440910d on prabirshrestha:langserver-vim into f57a807ba257d1c89be3dd05d262b3435bbd71bc on haya14busa:master.
Coverage decreased (-2.4%) to 80.917% when pulling d320a462dc82a48dea0a5581e3e53f5a1440910d on prabirshrestha:langserver-vim into f57a807ba257d1c89be3dd05d262b3435bbd71bc on haya14busa:master.
Thanks @prabirshrestha ! It looks interesting. I will check it later soon.
Coverage decreased (-2.4%) to 81.005% when pulling 3351ff24325722afe35f6cd028e5d0bb4202cc38 on prabirshrestha:langserver-vim into f57a807ba257d1c89be3dd05d262b3435bbd71bc on haya14busa:master.
Coverage decreased (-2.4%) to 81.005% when pulling 3351ff24325722afe35f6cd028e5d0bb4202cc38 on prabirshrestha:langserver-vim into f57a807ba257d1c89be3dd05d262b3435bbd71bc on haya14busa:master.
Coverage decreased (-2.4%) to 81.005% when pulling 2fc51dea173e0958a6b04486e264d7f306cdab6d on prabirshrestha:langserver-vim into f57a807ba257d1c89be3dd05d262b3435bbd71bc on haya14busa:master.
Coverage decreased (-2.4%) to 81.005% when pulling 2fc51dea173e0958a6b04486e264d7f306cdab6d on prabirshrestha:langserver-vim into f57a807ba257d1c89be3dd05d262b3435bbd71bc on haya14busa:master.
Is there any chance of this getting revived? It would be awesome to have a language server for viml!
@natebosch I believe @haya14busa is still waiting on me to fix lint issues. I haven't been able to have a look at this yet but if you are interested I would be more than happy to give you write access to my repo so that the issues can be addressed first.
Any update on this?
No updates from my side. Bit more details at here. https://github.com/haya14busa/go-vimlparser/issues/26
I do write vimscript a lot so if someone is willing to take this further I would be glad to help out.
I implemented completion for v: constants.

@haya14busa If you don't have enough time to do this, I can add some features to integrate to Vim script.
@prabirshrestha I created efm-langserver that is based on your langserver and haya14busa's errorformat. Thanks.
https://github.com/mattn/efm-langserver
Haven't tried it but this does seem promising. https://github.com/iamcco/vim-language-server