use in other ft & setting for Qiita

### use in other ft

I like [qfixmemo][] plugin and this use filetype like `howm_memo.markdown` that includes markdown syntax. I want use vim-markdown-quote-syntax in qfixmemo, so added a mechanism that you can set syntax in `.vimrc` with several filetypes.

[qfixmemo]: https://github.com/fuenor/qfixhowm

ex. use vim-markdown-quote-syntax in qfixmemo

```vim
augroup markdown_quote_syntax_for_howm_memo
  autocmd!
  autocmd Syntax howm_memo.markdown call markdown_quote_syntax#enable_quote_syntax()
augroup END
```

### specifying ft with Qiita syntax

[Qiita](http://qiita.com) use customized markdown that [can specify filenames of souces][ref].

[ref]: http://qiita.com/Qiita/items/c686397e4a0f4f11683d#2-1