Merge pull request #14 from ktbs/master

Additional modification to make framing work with multiple contexts
Initial check-in of new port of jsonld.js.
Pass expansion and normalization tests.
Pass compaction tests.
Pass all tests except frame embed overwrite.
Sort matches by @id.
Update to latest spec changes.
Allow null @id mappings, use null mapping in compact IRI.
Use %1.15e for double strings, fix base IRI handling.
Implement fromRDF and toRDF.
Fix whitespace regex.
Use RDF statements when normalizing.
Do better caching of statement hashes.
Fix bad indent.
Shorten some code with single line conditionals.
Remove special compaction of null-mapped IRIs.
Simplify if/else.
Always use @value in expanded form.
Update readme.
Readme fixes.