Upgrade ActiveRecord-JDBC-Adapter to master branch

Switch to master branch which provides Version 1.3.x of AR-JDBC adapter.
It strives to provide ActiveRecord 4.x compatibility (as well as still supporting 2.3 and 3.x) from a single code base. It's a recommended update for all AR-JDBC 1.2.x users.
Merge pull request #11846 from gaurish/jdbc-upgrade

Upgrade ActiveRecord-JDBC-Adapter to v1.3 for better compatibility with ActiveRecord 4
Updated outdated content in initialization guide