code: function defaultImageSrcGenerator(icon, options) {
  			return ''.concat(options.base, options.size, '/', icon, options.ext);
  		}
docs: Default callback used to generate emoji src
  based on Twitter CDN
  @param   string    the emoji codepoint string
  @param   string    the default size to use, i.e. "36x36"
  @param   string    optional "\uFE0F" variant char, ignored by default
  @return  string    the image source to use