Hard coded plugin directory is a big issue

Plugin works OK but had to be hacked around to do so: the plugin directory has been hard-coded into the plugin, which breaks the plugin if using anything other than wp-content as a directory name.

To fix, amend line 33 to read:

$viewer_base_url= plugin_dir_path( __FILE__ ) . '/web/viewer.php';

Otherwise, still working in WP 4.2.2, which is useful.