Add multi favicon support
FAVICONS can be empty in conf.py, so add the default value in Nikola.__init__
Update other base_helper.tmpl
Update changelog and authors.
Merge remote-tracking branch 'upstream/master' into feature_branch

Conflicts:
	CHANGES.txt
	nikola/nikola.py
Merge pull request #256 from zhaojunmeng/feature_branch

Add multi favicon support