Twitter API v1.1 search

Some changes to get search working again in Twitter API v1.1.

I didn't strive to do a complete job (I don't think my Common Lisp skills are up to the job yet), but I did enough to get it working for hashmoot.com.

Some things to note:
* Searching works, at least the way I use it.
* Instead of returning search results, the Twitter API now tries to be consistent in returning Tweets and Search Metadata. I changed the search code so it now returns the same tweet objects as other calls. This seems a nice change for the API but it does mean the new API won't be backwards-compatible. Classes/elements 'search-ref' and 'search-ref-metadata' are no more.
* Authentication is necessary for all API calls now (including search).
* Calls to get-user (which is used during OAuth setup) now requires authentication... This caused me some grief, so I put in a nasty hack to get it working. It's a very nasty hack, and someone who knows what they're doing should probably fix it. It's marked as a hack in the cl-twit-repl/twitter.lisp file in functions repl-authenticate-user and get-authenticated-user.
* Rate limiting has changed, and I never bothered fixing that. Search macros like do-search and with-paging still don't work though.
* Finally, there seem to be more changes in the diffs than I made because I have Emacs set to trim whitespace at the end of lines. This works well for me, but I don't know if you have a diff mechanism that ignores whitespace to help you with the merge.

Many thanks,

Geoff