remove tdiary-cache-memcached
remove rdb adapter and specs
added IO namespace.
remove broken hooks
rename IO classname
Revert "remove tdiary-cache-memcached"

This reverts commit 947299b3f9ac2b4c6e099430333ce025660ca8e3.
remove rdb spec task from travis
remove rdb from test suite
Merge pull request #383 from tdiary/remove-rdb-plugin

Remove rdb plugin
bump version to 4.0.1.20131102
fix namespace of Comment
added TDiary::IO::Default specs
added TDiary::IO::Default#transaction specs
fix spec failure when running with unique file
separated initialization of IO and Cache adapters