without meta=true static JRuby methods are not picked up on meta-class
[postgres] ColumnDefinition.array? method is used by SchemaCreation

all credits to @leogavidia - closes #474 : 
undefined method array? in ActiveRecord::ConnectionAdapters::PostgreSQLAdapter::ColumnDefinition
Add change_column_test for mysql
need change_column even when SchemaCreation is used (closes #475)
share (change column) test methods between H2/MySQL
running change column tests with postgres (as well) should not hurt
move PG_VERSION since it's only used in one test case + tune jdbc config
support for running test againg MySQL/PostgreSQL using **adapter: jdbc**
minor README updates
[postgres] we should return "raw" hstore values on AR < 4.0 by default
(regression caused by fixing #454 for AR >= 4.0)
avoid using PG_VERSION in a test-case (since global const was moved)
Added failing test for multiple savepoints
when "pop-ing" current savepoint name - consider open transaction count

- this allows us to work with user marked savepoints as intended, since they will likely execute within a single AR transaction object
- but at the same time AR's nested transaction emulation (using savepoints) will work in a Rails compatible way (fixes #477)
re-build jar - prepare for 1.3.2