added filename to Browse button in upload.html

Adressing Issues #12 and #26.
12: On the upload screen, after a review file is selected to be uploaded, this commit displays the name of the file to be uploaded.
26: Adding a ratings property to upload.html and parsing it in views.py to prevent empty return values when trying to access review.overall_review.stars. This keeps the main page from crashing but doesn't adress the newly created project page as it would need stars values for each category (review.documentation_review, review.ease_of_use_review etc).