To automatically send out a new tweet every time you post a new article to your Jekyll blog, first, get the link to your RSS feed. Then, sign up for If This Then That (IFTTT) and create a new recipe. Make the trigger ‘Feed’ and add the link to your RSS feed. Next, link your Twitter account as the action for the recipe, and it should have some default values to add the title and the URL of the post.
Every time you add a new post it should send a new tweet out a few minutes later.