Fix missing possibility of assigning a CSS-class

Due to the missing pattern "%s" in the property
  protected $messageOpenFormat = '<ul%s><li>';
it was not possible to set a class in ViewScript via
  $this->formElementErrors()->setAttributes(array('class' => 'my-errorlist-class'));

If you do nothing the default value for css-class "help-block" is kept.
Merge pull request #70 from fg-ok/patch-1

Fix missing possibility of assigning a CSS-class
Update TwbBundleFormRow.php
Update .travis.yml
Update .travis.yml
Update phpunit.xml
Fixes ->form()->openTage($form) usage

Makes it possible to use ->openTag to render the form using correct layout classes.

Examples:

<?php echo $this->form()->openTag($this->customerForm); ?>
<?php echo $this->form(null, 'inline')->openTag($this->customerForm); ?>
Update expected rendering to match with rendering of last version of ZF2
Merge pull request #72 from maurice2k/patch-1

Fixes ->form()->openTag($form) usage
Add button groups support
Merge origin/master
Improve label position support
Improve label position support
Add test for checkobx helper, update readme
Fix typo in readme file.
Merge pull request #76 from PhilETaylor/patch-1

Fix typo in readme file.
Supports "disable-twb" option for checkbox elements
Update composer.json
Added missing parentheses in README.md
Merge pull request #78 from webdevilopers/master

Added missing parentheses in README.md