Require URIs to be absolute to be valid. This fixes issue #122.
In RDF::Writer.dump/buffer/open: Set external_encoding based on :encoding option if it is not otherwise set. Also, if no :encoding option is given, but the IO/StringIO file has an external_encoding, use that as the default for output encoding. This relates to issue #111
In NTriples::Writer, If encoding is ASCII, do not use \b or \f output escapes.
Added Statement#pattern? which returns true unless all elements are Resource or Literal as appropriate. This is used in Mutable#delete to check for patterns when deleting.
Make Reader#lineno public, not protected.
Release 1.1.0.p1