If you’re like me and get a lot of requests to make SharePoint sites responsive (it is 2016 afterall!), here’s a great read and some excellent resources courtesy of the SP Patterns & Practices team to make your life a little easier: http://dev.office.com/blogs/announcing-responsive-ui-package-for-sharepoint-on-premises-2013-2016
Looking for the SharePoint Online version? That can be found in the PnP Partner Pack:
Happy (responsive) designing!