Paramaterize widget width; fix JS typo (#821).

- Widget width can be set via data-width attribute (parallel to
  data-height).
- Fix typo in definition of trim polyfill (caused widget to
  fail in IE8).
Widget layout improvements; IE8 compat (#821).

- Use background image and background-size techniques to layout
  images in browsers that support background-size.
- Tweaks to breakpoints and responsive design.
- Widget basically working in IE8. Much of this commit involves
  changes to support IE8.
- Open issues:
  - Some more tweaking of sizing and layout would make the widget
    look better in some sizes across all browsers.
  - Media queries do NOT work in IE8 when widget is in iframe, even
    with css3-mediaqueries.js. This is the case when CSS is inline
    as well as when linked via file. Respond.js *may* work where
    css3-mediaqueries.js does not.
  - IE8 detection for CSS-based fixes in the LESS file is done via
    modernizr's no-backgroundsize class on html. This is not really
    appropriate use of the class. Conditional inclusion of fixup CSS
    files is probably more appropriate, but I'm not sure if the
    overhead of that is worthwhile.
Better header/footer CSS; footer links (#821).

- Use table/table-cell technique to vertically align header and
  footer items even when multi-line.
- Related item links in footer are interleaved between projects
  and organizations, trailing comma problem fixed.
- Don't limit vertical size of images within list items (list items
  will clip).