Release 3.0.2

Improvements to vocabulary generation:

• Only use english or plain terms, as Ruby serialization does not preserve language.
• Use lists for top-level values as well as embedded.
• Order embedded property values.

In Reader.open, ignore content_type if it is 'text/plain'. This allows us to fall back on file_name and/or sampling.

Update documentation on URI#join and URI#/ to clarify how arguments are treated.