added a CSS Reset: normalize.css
PLACEHOLDER: in the process of dealing with a logic bug where the groups model doens't stay in sync with the view. A fix was added to the post-group.  But, the height of the group DOM element is still not updating at all times
the group height and offset are recalculated nd the group model is updated whenever a post-it is dragged from within a group
post-its inside a group now reorder according to the group model--resulting in all posts shifting up when one is dragged from inside the group DOM.
Merge pull request #3 from theInternauts/post-groups

Post groups