wildignore support

[yacut]

I would like to set wildignore in init.vim or .vimrc and does not have it in the search results.
For example:

" ignore npm packages
set wildignore+=**/node_modules/**

[brooth]

I've got to say that it's quite complex task. It works out of the box for default (vimgrep) source, but to transform wildignore to ag/ack's pattern is a tricky task. I'll try to solve it in beta 3.
Now there are 2 options:

1. command parameter:

:F foo \.js --source=ag --ignore=node_modules

2. vimrc:

let g:far#sources = {
    \   'ag': {
    \       'args': {
    \           'cmd': ['ag', '--nogroup', '--column', '--nocolor', '--silent',
    \                   '--max-count={limit}', '{pattern}',
    \                   '--file-search-regex={file_mask}',
    \                   '--ignore=node_modules']
    \       }}}

[yacut]

Thanks, it helps.