If using gulp-livereload without a browser extension, run this task in development mode to automatically inject the required script tag:

var insertLines = requir('gulp-insert-lines');

gulp.task('livereloadTag', function () {
    gulp.src('/path/to/template.html')
        .pipe(insertLines({
            before: /<\/body>/,
            lineBefore: '<script src="http://localhost:35729/livereload.js"></script>'
        }))
        .pipe(gulp.dest(distPath));
});