Change size of story previews and upgrade jQuery to 2.0 line

Change story previews to show a certain number of characters or
paragraphs and upgrade jQuery to 2.0.3, consequently dropping IE8
support (I didn't really have it anyway)
Look and feel improvements

Change some css including removing fallbacks for font sizes specified
in rem and change and the amount of text displayed for previews. Also
make monk functions accessing mongo return their promise when possible.