use the _selector changes api instead of js filter
use the _selector changes api instead of js filter

CouchDB 2.0 has a new API for simple filtering based in `_selector`s.
see docs at: http://docs.couchdb.org/en/master/api/database/changes.html#filtering

this obsoletes `couch/filters/channel.js` but I'll leave it for backward
compatibility

gdamjan/irclog-couchapp,gdamjan/irclog-couchapp