improv: add editorconfig

See http://editorconfig.org/ for more informations about what is EditorConfig
docs: add reference for EditorConfig
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.
Merge pull request #84 from sharnik/master

Add --ignore-case switch to silver searcher.