Create default document type in Sublime Text

SublimeTextDefaultHTML

Make default document Sublime Text 3 creates is HTML

Go to Tools -> New Plugin

Then paste this over the file, hit save and call it "DefaultHTML.py" or whatever you like

import sublime, sublime_plugin

class EverythingIsHTML(sublime_plugin.EventListener):
   def on_new(self, view):
      view.set_syntax_file('Packages/Text/Plain text.tmLanguage')
Of course, you can change the language from HTML to ... whatever you prefer. You just need the relative path to the tmLanguage. You can get that by opening a file in your favorite language and then open the console (View->Show Console) and type:

view.settings().get('syntax')