support phpunit 3 and 4

Closes: #7, #8
Merge branch 'allow-phpunit-3-and-4' of github.com:jrobeson/SymfonyConfigTest into jrobeson-allow-phpunit-3-and-4
Configure Travis to test different versions of SF and PHPUnit
Merge branch 'jrobeson-allow-phpunit-3-and-4'