applies flat-ui for session#welcome using absolute top to center text
styles teacher and student with background color and vertical border to simplify design

chose to use absolute positioning for the left section because then top and bottom 0 can be used to create a vertical border that expands the page. Also, a fixed width is given to the login form with text-align right, which prevents the page from being responsive as it stands. Maybe fix later, for now it's fine.
adds repeating tile background to add texture to site