/r This request handler returns the revision history (newest-oldest) for all translations associated with a particular source text. The results can be filtered by source language, target language, or domain. It assumes that other filtering criteria will be applied by the requester. It expects the following parameters: st = source text (utf8 encoding) sl = optional source language code tl = optional target language code domain = optional domain to limit results too (e.g. foonews.com) output = output format (json, xml, rss, po, xliff)