Assuming you have the following static page URL structure for all pages (you will need to disable the breadcrumb inside your blog pages).
UPDATE 2015-05-06: You can use markdown files now too.
You can use the following liquid statement which will render a breadcrumb with url and text from the frontmatter. Make sure all your pages have page.breadcrumb set to the value you want to be shown inside the breadcrumb element.
Example page with frontmatter:
Now here is the code for the breadcrumb
UPDATE 2016-03-14: The active class is now correctly set on li element.
The output will be a breadcrumb for bootstrap. You will need to style the html with css.
You can see a full demo project here: github.com/comsysto/jekyll-breadcrumb-for-github-pages/