Merge pull request #81 from AdrienGiboire/master

editorconfig
filetype on before filetype off, for git&svn comment editing.
Merge pull request #83 from newclear/master

filetype on before filetype off, for git&svn comment editing.
Add --ignore-case switch to silver searcher.
Merge pull request #84 from sharnik/master

Add --ignore-case switch to silver searcher.
improv: set shell to ZSH in interactive mode

In interactive mode, ZSH will read `~/.zshrc`. Else, it will first stick to
`/etc/zshenv`, then `/etc/zprofile` and last to `.zshrc`. Without this, running
shell command from within Vim may result in `command not found`.