create.html: adding screencast, fixing typos
create.html: adding screencast, fixing typos

The /create page now links to a short tutorial on linking sheets to TimeMapper.

This commit also fixes a few things in the "anonymous creation" section.
okfn/timemapper,kuansim/timemap,kuansim/timemap,okfn/timemapper,kuansim/timemap,ukris/timemapper,ukris/timemapper,ukris/timemapper,okfn/timemapper