cleanup test execution
 - use phpunit installed from composer
 - lowercase tests/Bootstrap.php -> tests/bootstrap.php
 - moved phpunit --strict option to phpunix.xml
 - run coveralls without directly from .travis.yml
 - run tests with PHP 5.3.3 using travis-ci (requires --prefer-source)
 - added "composer self-update" to "before_script"
exit(1) on test execution if not installed
Merge pull request #17 from marc-mabe/testsCleanup

Tests cleanup