Update for version 1.1 of Twitter's API (fixes #49)

This commit:

* switches response parsing from HaXml to aeson (since the new API only uses JSON)
* removes the lsrt and lsrtarchive commands (since the new API doesn't seem to distinguish them from lsrecent and lsarchive, and those commands now include both original tweets and retweets)
* updates the setup command to set urlbase to %(serverbase)/1.1

There are two small changes that aren't strictly related to the API update:

* fixed truncated retweet text (the JSON document now includes a retweeted_status object which contains the original tweet content); and
* added a "status" command to retrieve a single tweet by its id.

I can pull one or both of those changes out if you'd prefer to deal with them separately.

To try it out, you'll need to either run twidge setup again, or manually adjust the urlbase configuration property in your .twidgerc file.

I think I've tried everything out at least briefly, but it'd be good to hear from others testing this. In particular, the paging logic has changed in two different ways in the new API (ie, the message commands like lsrecent and lsdm with the -a option have slightly different behaviour to lsfollowing etc).

Caveats:

* I've switched aeson for haxml in the debian/control file, but I haven't attempted to build the Debian package.
* I haven't considered how this affects compatibility with status.net