Update Grafitti-simple to use Ojwidgets and remove o'Closure.
This commit also fix some stuff regarding values injection, to follow the latest version of Eliom.
Change visible argument to an alpha argument directly
Remove get_element and use value injection to retrieve slider instead
Remove useless coercion on size_slider
Move css folder to the correct location
Update CSS for graffiti-simple
Add deriving.syntax package to the Makefile
Merge pull request #2 from Engil/master

Update Grafitti-simple to use Ojwidgets and remove o'Closure.