Changes for DLTP-187

Header changes:
 * Comment out beta ribbon.
 * Change "Hesburgh Library" and associated link to "Office of the
   Provost". This change was made in both the sufia.en.yml file and in
   the _brand_bar.html.erb file in order to get the correct text
   formatting.
 * Fix Login button on screensizes less than 768px

Footer changes:
 * Hesburgh Library logo and link to right side of footer.
 * Remove some text from the left side of the footer.
 * The build identifier is still in the html of the page, but is
   commented out so that it only appears in the source code.