Release Name: 0.0.6

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


Changes:
* Supported groonga 0.1.1.
* Fixed documents [id:mat_aki]
* Supported groonga expression for searching.
* Added API
  * Groonga::Table#union!
  * Groonga::Table#intersect!
  * Groonga::Table#differene!
  * Groonga::Table#merge!
* Provided tar.gz [id:m_seki]
* Fixed memory leaks