Cleaned up coding conventions and hard tabs.
Implemented the SPARQL::Client.serialize_value method.
Implemented the SPARQL::Client.serialize_uri method.
Ensured that RDF.type in the predicate position gets abbreviated to
'a' per the SPARQL grammar, while still supporting the non-abbreviated
behavior when passing in an uninterned copy of RDF.type.
Fixed two specs that were broken by the previous commit.
Implemented the SPARQL::Client::Query#graph method.
Replaced all references to the SPARQL 1.0 spec with 1.1 equivalents.
Switched to using the HTTP POST method instead of HTTP GET in order to
avoid problems with longer query strings.

If need be, the previous behavior can be restored as follows:

    SPARQL::Client.new(endpoint, :method => :get)
Implemented the SPARQL::Client#headers attribute accessor.
Refactored the SPARQL::Client#request method implementation.
Updated the gemspec information.
Ensured that the SPARQL::Client specs still pass after recent changes.
Defined the SPARQL::Client::RESULT_BRTR and ACCEPT_BRTR constants.
Bumped the version to 0.3.3.
Corrected my email address in the AUTHORS file.
Implemented 'application/sparql-query' support for SPARQL 1.1 endpoints.

This is a feature introduced in the SPARQL 1.1 Protocol specification
whereby the SPARQL query string may be submitted directly as the body
of the HTTP request, avoiding the complication and time/space overhead
of URL encoding/decoding the query string as was required by the
previous version of the protocol.

For maximum compatibility, this client implementation still defaults
to using the SPARQL 1.0 protocol; to enable the new 1.1 protocol
support, configure your SPARQL::Client instance as follows:

    SPARQL::Client.new(endpoint, :protocol => 1.1)

See: http://www.w3.org/TR/sparql11-protocol/#query-via-post-direct