add option to disable setting include

[cdepillabout]

It would be nice to add an option to disable setting include:

purescript-vim/ftplugin/purescript.vim

Lines 2 to 3 in 67ca4dc

	setlocal include=^import
	setlocal includeexpr=printf('%s.purs',substitute(v:fname,'\\.','/','g'))

Setting include causes keyword completion to take a very long time to finish. Keyword completion is triggered with Ctrl-P or Ctrl-N in insert mode. There doesn't appear to be any caching of files processed for keyword completion, so it basically becomes unusable when there are multiple imports in a PS file.

As a workaround, it is possible to disable keyword completion from included files with a line like the following:

autocmd FileType purescript setlocal complete=.,w,b,u,t

Here is the documentation for the complete option:

http://vimdoc.sourceforge.net/htmldoc/options.html#'complete'