How to add Redactor Image resizing and positioning to the Rich Text field in Craft?
If you're on Craft 2.6.2950 or greater, it includes Redactor II 1.3.1, where they re-introduced image resizing and positioning support. 

You'll just need to add:

imageResizable: true,
imagePosition: true


to whatever craft/config/redactor config file your Rich Text field is set to use under its settings.