環境： linux ruby1.9.2 rails 3.0.5 mysql2 0.3.2
遇到問題：Please install the mysql2 adapter: `gem install activerecord-mysql2-adapter`
解決方法:
gem uninstall mysql2then
gem install mysql2 -v 0.2.7
參考：http://stackoverflow.com/questions/5840742/version-of-mysql2-0-3-2-doesnt-ship-with-the-activerecord-adapter-bundled-anym
“The problem is because you are trying to install the lastet version of mysql2 wich is incompatible with rails 3.0.x version ”
做ROR, 版本的問題 真讓人頭疼
