Separate form error classes from other classes

Some projects want the ability to use abide and display errors with the default
error styling, but not include foundation's defaults for input and select styling

This commit adds a variable $include-html-form-error-classes that will include
the error classes separately, thus letting us use abide independently.
Update CHANGELOG.md
Missing variable from docs

Causes dropdown label to be inconsistent when excluded.
Remove check for loaded images in Interchange as this should be the user's decision.
Merge branch 'master' of github.com:zurb/foundation
Conform syntax to non-underscore methods in Interchange.
Update CHANGELOG.md
Fix closing tag in section docs
Merge pull request #3343 from mfeckie/master

Missing variable from docs
Merge pull request #3328 from ziad-saab/separate-form-classes

Separate form error classes from other classes
Updated normalize to v2.1.3

Taken in account the custom changes made to the file. See #3056 or commit f3f10f2
Merge pull request #3360 from MekZii/patch-1

Updated normalize to v2.1.3