Bootstrap with Flexslider jQuery Issue

The code you wrote is NOT including the flexslider code, it is only trying to include a google hosted copy of jquery.

wp_register_script( 'flexslider-jquery',
  # this is just the Google Hosted version of jQuery
  'https://ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.min.js',
  '', true );

You probably want something more like this:

wp_register_script( 'flexslider-jquery',
  get_template_directory_uri() . '/js/jquery.flexslider-min.js',
  array( 'jquery' ), false, true );

You’ll need to put the flexslider code in the right directory of course, or adjust the above to match your site structure.