Syncs styles with h5bp styles

- Updates styles to sync with updates in the HTML5 Boilerplate default
style set.
- Removes IE6/7 Styles that were unused.
- Removes Image Replacement class that were unused.
- Removes Chrome Frame class that was unused (plus Chrome Frame is no
longer supported).
Merge pull request #630 from codeforamerica/hb5-styles

Syncs styles with h5bp styles