Enable testing of php 5.4 on travis
Issue #1841324 by ergonlogic, greg.1.anderson, anarcat: Requiring php 5.3.5 for Drush is premature.
Issue #2029493 by helmo: Fixed testBackendMethodPost fails on php 5.4.

Now it fails properly
Issue #2029493 by helmo: Fixed testBackendMethodPost fails on php 5.4.