made text plugin work with my sane-add-plugin branch on ojii/django-cms
added guard against cms version for new add-plugin
fixed pre-3.1 compat mode
LooseVersion is weird, check for pre 3.1 via feature detection
Merge remote-tracking branch 'origin/master' into sane-add-plugin

Conflicts:
	djangocms_text_ckeditor/cms_plugins.py
Merge pull request #179 from ojii/sane-add-plugin

Sane add plugin for divio/django-cms#3516