replaced path.exists with fs.exists
replaced path.exists with fs.exists

When generating a styleguide with grunt-styleguide using styledocco it
throws an error:
path.exists is now called `fs.exists`.

ooooooo-q/styledocco,ooooooo-q/styledocco,trungnghia112/styledocco,paulwellnerbou/styledocco,paulwellnerbou/styledocco,trungnghia112/styledocco,jacobrask/styledocco