Add tex completion for deoplete

vim/ftplugin/tex.vim

@@ -5,4 +5,11 @@ if !has("nvim")
                 \}
 endif
 
+if has("nvim")
+    if !exists('g:deoplete#omni#input_patterns')
+        let g:deoplete#omni#input_patterns = {}
+    endif
+    let g:deoplete#omni#input_patterns.tex = g:vimtex#re#deoplete
+endif
+
 set conceallevel=0