- Remove some unnecessary code: IsHeaderFile is no longer required, as the logic
to find flags to headers is now built into YCM
- Add function to make paths in flags absolute: It seems YCM is not correctly
resolving paths in flags to consider `build` as the compiler working
directory.
- Update documentation.
"vimrc" refers to all files that are used to configure Neovim. The main
configuration file is init.vim nowadays.
All nvimrc references that are left refer to a local ".nvimrc" which is read
if 'exrc' is set. ".ngvimrc" references were completely wiped.
Closes#3552.
