Made default class optional. Fixed some more SASS issues. Needs more
work.
More SASS edits for tabs.
Merge branch 'v4.0' of https://github.com/wet-boew/wet-boew into v4.0
Merge branch 'v4.0' of https://github.com/schindld/wet-boew into v4.0

Conflicts:
	src/plugins/tabs/tabs.js