Reverted workaround for travis-ci.org

Fix was published on travis-ci.org, so the workaround is no longer necessary.
Reverts c0319b1b4aabfc26d6baf6fa17424cfe2cf1855f, 2a6dfe97c62b332e9a9e5aa7b0f8ee604ea28c35 and a3a088d3f9a80f0f829ebd37c47cd7fba0294f01. Refs #63.