chore(travis): Switched to blacklisting not-tested branches instead of whitelisting

For details see: http://docs.travis-ci.com/user/build-configuration/#Specify-branches-to-build

Fixes: #6851
chore(composer): Added validation of composer.json and necessary fields to pass validation
Merge pull request #6853 from Srokap/ticket_6851

chore(travis): Switched to blacklisting not-tested branches instead of whitelisting
Merge pull request #6854 from Srokap/composer_validate

chore(composer): Added validation of composer.json and necessary fields to pass validation
chore(release): Improved version control in release script as well as error handling.

Fixes: #6850