How to decide whether to publish masters project in computer science alone or with supervisor?
As a master student, or even Ph.D. student, there is nothing wrong on writing a paper with your supervisor(s). In fact, it shows your group work ethics. You should be delighted an experienced academic put his/her name next to yours on a publication. It adds value to the publication, because your supervisor is more well known than you and others will discover your publication faster. 

You should think about being an independent researcher; at the later stages of the research (e.g., as a postdoc or an academic).