Add hide_input.js. It implements an extension that hides/unhides selected cells.
use get_selected_cell and assume only one cell can be selected at a time.
use input_collapsed instead of collapsed, which is used by the method that collapses the ouput of a code cell.
make use of toggle on the input div.
Merge pull request #13 from bjanssen/master

Add hide_input.js.It implements an extension that hides/unhides selecte...