rroonga version 1.0.4 has been released!

rroonga is a extension library to use groonga's DB-API
layer. rroonga provides Rubyish readable and writable
API. You can use groonga's first and highly functional
features from Ruby.

Changes:

### Improvements

* Supported groonga 1.0.4.
* Added Groonga::UnsupportedCommandVersion.
* Added Groonga::Record#support_sub_records?.
* Added Groonga::Record#eql?とGroonga::Record#hash.
(treat two the same table and the same record ID object as the same Hash key.)
* Supported pkg-config gem.
* Supported generic #record_id object handle for custom record object
in Groonga::Table#select.
* Added Groonga::Record#record_id.
* Added Groonga::Table#support_key?.
* Added Groonga::Record#support_key?.
* Added Groonga::Record#support_key?.
* Added Groonga::Column#reference_key?.
* Added Groonga::Column#index_column?.
* Added Groonga::Schema#dump.
* Supported multi columns index creation in Groonga::Schema.
* Supported meaningful path in Groonga::Schema.
* Made reference table omissible when index column definition
in Groonga::Schema.
* Added Groonga::Schema.remove_column.
* Added convenience timestamps methods to define "created_at" and
"updated_at" columns in Groonga::Schema.
* Added Groonga::Context#support_zlib?.
* Added Groonga::Context#support_lzo?.
* Added Groonga::Database#touch.
* Added Groonga::Table#exist?.
* Added Groonga::Record#valid?.
* Added Groonga::Column#vector?.
* Added Groonga::Column#scalar?.
* Added Groonga::Record#vector_column?.
* Added Groonga::Record#scalar_column?.
* Accepted any object that has record_raw_id method for record ID required
location. Groonga::Record isn't required.
* Added Groonga::Record#record_raw_id.
* Accepted any object that as to_ary method for reference vector column value.