HTML code to PHP code mapping does not work
You have the smallest of errors in your code; in the very last line you're trying to interpolate a variable into a string using single quotes. You need to use double quotes instead:

drupal_add_js('similetimeline',"$timeline_lib_path/timeline_js/timeline-api.js");


Have a peek at the PHP Strings Documentation for more information.

I've just noticed another problem actually; you don't seem to be using drupal_add_js() properly. The first argument should be the name of a file or an inline string, in which case you should specify that it's inline:

drupal_add_js($timeline_inline_js, 'inline');
drupal_add_js("$timeline_lib_path/timeline_js/timeline-api.js");