Release Name: 1.0.0

Notes:
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:
* Supported groonga 1.0.0.
  * Added Groonga::CASError.
  * Added :order_by option to Groonga::Table#open_cursor.
  * Added Groonga::PatriciaTrie#open_prefix_cursor that creates a cursor
    to retrieve each records by prefix search.
  * Added Groonga::PatriciaTrie#open_rk_cursor that creats a cursor to
    retrieve katakana keys from roman letters and/or hiragana.
  * Added Groonga::PatriciaTrie#open_near_cursor that creates a cursor to
    retrieve records order by distance from key.
* Supported _key as index source.