Add support for table caption

Provides styling of table caption element
Provides more configuration of side nav

Adds a few more variables to configure headings and link hover background
Update _offcanvas.scss
Merge pull request #5104 from winghouchan/reverse-c1c81b

Reverse c1c81b
Fix #5155

Fix #5155. Hamburger icon has now become a pseudo-element meaning the old way of centre positioning it will not work. Updated version will work.
Merge pull request #5159 from winghouchan/fix-5155

Fix #5155
Fix for issue #5036
Merge pull request #5160 from darylprickett/issue_5036

Fix for issue #5036
Allow controlling heading sizes on small screens

Introduced variables $h1-font-reduction etc to allow customizing font sizes on mobile separately without overriding them in a custom stylesheet.
Merge pull request #5170 from danielck/master

Allow controlling heading sizes on small screens, fixes #5169
Merge pull request #5033 from clyates/patch-5

Provides more configuration of side nav
Merge pull request #5032 from clyates/patch-4

Add support for table caption
adfix for overriding styles on subheader
undo PR 5128 as it was a breakig chnage
Merge pull request #11 from zurb/master

Update Foundation