section_footer clearfix fix

use the clearfix class on the container of the floated elements, instead of a br with a clear after
remove extra div around nav_icon

the nav icon rules work on the icon itself, don't need a div inside an anchor
delete some unnecessary rules

display inline-block not necessary in a float.
setting width on float in float doesn't do anything.
reduce negative margin by eliminating padding

no point in having a negative margin crawl over padding
set a width on previous_section and next_section containers

this is the only way to prevent word-wrap on long section titles

@TODO: replace anchor with div, and nest anchor inside of div so the link isn't 50% of the container, but the width of the text.
add missing ID param for hidden sections

hidden sections were only getting passed a class and not an ID, messing up styles
update all course formats to proper clear fix
Merge pull request #65 from thedannywahl/fix_section_footer

cleanup section footer