dropshadow example wasn't showing up in firefox
dropshadow example wasn't showing up in firefox

Fix issue https://github.com/benfred/venn.js/issues/74 . Seems
to be caused by having the div with the example having the same
id as the filter ('dropshadow'). Renaming makes this work again

benfred/venn.js,sherbert-lemon/sherbert-lemon.github.io,benfred/venn.js,benfred/venn.js,sherbert-lemon/sherbert-lemon.github.io,sherbert-lemon/sherbert-lemon.github.io