Add content in the <head> area
I would like to add a Google Tag Manager script to the page so that we can take advantage of the various Google services (Analytics, Webmaster Tools, etc). Is there a way to add this script to the <head> of every page? Or somewhere else like just before the closing </body>? I am aware I could modify the layout and add a custom script but this does not add content to non-editable pages (eg. the article page).