add sqlite3 to devDependencies
use DATETIME type for MySQL/MariaDB

for MySQL/MariaDB, TIMESTAMP is not an ideal type.
http://stackoverflow.com/questions/409286/datetime-vs-timestamp

And even worse, causes syntax error on CAST.
stop quoting identifiers in raw SQL since there is no SQL standard to quote unfortunately
add mysql optimized query
Merge pull request #3 from twada/mysql

MySQL support