bump to 5.1.1 and update changelog

fix bug with ruby sass where sass variables can be defined in conditi…

…onal (works in libsass though)

Merge branch 'master' of github.com:zurb/foundation

Merge branch 'master' of github.com:zurb/foundation

Merge branch 'master' of github.com:zurb/foundation

bump version

more cleanup

Version 4.3.2

Version 4.3.1

Version 4.3.0