Merge pull request #125 from drywall/hotfix/tinymce

Eliminating hard-coded URLs in tinymce plugin
incorrect field name
Testing and fixing series/categories related logic
Implementing read next/related widget
Fixing error_notice on metabox api
Merge branch 'master' of https://github.com/INN/Largo into feature/related-widgets
Merge pull request #129 from drywall/feature/related-widgets

Implementing new widget for 'read next'