tunnings for rake tasks on 4.0 (should now be working for built-in adapters)
update 4.0 and start testing agains AR-4.0 with travis-ci
refactored JdbcConnection - eliminated ConfigHelper + moved #active?
JdbcAdapter + connection tweaks
- support passing 2 args to #initialize
- do not force adapter_spec if set to nil
- prepare for doing #configure_connection on #reconnect!
- no need to #configure_connection when spec module extended
jdbc connection updates to better follow AR semantics
- active? should check whether connection is valid
- reconnect! should configure_connection if available
- use connection.isValid as fallback (no need for connection_alive_sql)

fixes #351
connection_alive_sql for sqlite3 - it's driver is not very  recent
thus likely not conforming to all of JDBC 4.0