deoplete-clang doesn't complete include content unless I reopen the file.

## Problems summary

I'm using the deoplete + deoplete-clang + neoinclude. When my file `#include ` and
I typing `INT` it will not show any completion candidates. If I reopen that file and typing `INT`
it will show completion candidates like `INT_MAX` and `INT_MIN`.
## Expected

Completing include content without reopen the code file.
## Environment Information
- OS: Arch Linux
- Neovim version: 0.1.4
## Provide a minimal init.vim with less than 50 lines and not plugin manager (Required!)

``` vim
" Your minimal init.vim
set runtimepath+=~/path/to/deoplete.nvim/
set runtimepath+=~/path/to/deoplete-clang/
let g:deoplete#enable_at_startup = 1

" Use smartcase
let g:deoplete#enable_smart_case = 1

" Let also do completion
inoremap pumvisible() ? "\" : "\"

"close the preview window after completion is done.
autocmd CompleteDone * pclose!

" completion bracket
call deoplete#custom#set('_', 'converters', ['converter_auto_paren'])

" Deoplete-clang
let g:deoplete#sources#clang#libclang_path = '/usr/lib/libclang.so'
let g:deoplete#sources#clang#clang_header = '/usr/lib/clang'
```
## The reproduce ways from neovim starting (Required!)

``` c
#include
INT //will not show any completion candidates
```

**save and reopen that file**

``` c
#include
INT //will show completion candidates like INT_MAX and INT_MIN
```

I'm not sure it's deoplete-clang or other plugin's problems.
Thanks for any help.