Remove regression tag from new tests

Regression tags should only be applied to tests running in the
previous release. New tests for newi features by default should not have
the tag regression, unless they are incorporated into the latest
stable branch. This change updates the tags accordingly.

In addition, this commit does minor changes in README file.

Change-Id: Icca6c15343961fee1bb1adf0ee19f6871725f9cf
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>