Give warning if running on older utPLSQL #70

When I tried running test via SQLDeveloper extension on utPLSQL v3.1.2 I got surprised by lack of test window.

It would be nice if we could get some info/warning to users that would inform them why tests are not running with nice new UI.
Even something like a comment in SQLDeveloper worksheet would be great to say:

-- Running with SQL worksheet
-- detected utPLSQL v3.1.2.2130
-- you need utPLSQL v3.1.7 or above to use the test-runner UI
EXECUTE dbms_session.reset_package;
SET SERVEROUTPUT ON SIZE UNLIMITED
CLEAR SCREEN
EXECUTE ut.run('UT3$USER#');