Sanitize search string to prevent XSS vulnerabilty
Non-kitten search options, bugfixes, github/gittip links

- added dropdown to choose something other than kittens

- fixed error with random math when there are fewer than 100 images
returned (happens if you specify your own search term)

- Made "about" text more visible and added links to github and gittip.

- a little minor refactoring and internal rejigging
Added additional licenses (BY-SA, Flickr Commons)

Based on code by cincodenada; see https://github.com/Skud/writtenkitten/pull/2

Also added a CONTRIBUTORS.md (to allow for recognising contributions by
people that github doesn't show for whatever reason)
Removed otter and cupcake options.

Sigh. Too much noise in the stream.