Update stylesheet.css

Added a few tiny css changes to add some more responsiveness.
- The '.gallery-media-full' padding makes sure that the comment, etc...fields are not 'right against the left border'.
- The extra line '.taggable' overrides the default width of the image, when resizing (or mobile viewing) the photo was not resizing along with the screen.
- The lineheight change (550px -> 100%) in .gallery-media-full-view makes sure there isn't a gap as the main image resizes.

Feel free to merge, or not if you don't like it.
Cheers, Dries