fix DataAccess test on HHVM
add travis build matrix for all built-in PostgreSQL versions
exclude unsupported HHVM + PostgreSQL and HHVM + Mysqli from travis build matrix for now
Merge pull request #501 from deeky666/disable-travis-hhvm-unsupported-drivers

Exclude HHVM + PostgreSQL and HHVM + Mysqli from travis build matrix
Merge pull request #498 from deeky666/add-travis-postgresql-versions-build-matrix

Add travis build matrix for all built-in PostgreSQL versions
Merge pull request #495 from deeky666/fix-hhvm-data-access-test

Fix DataAccess test on HHVM