test against php 5.6

[smsaladi]

Does raintpl3 support php5.6? If so, that would be nice. I would suggest adding this to the .travis.yml

[smsaladi]

On that note, is there support for the php 7 series? Might suggest adding those to the .travis.yml file too (if so).

[mirabilos]

It certainly works on PHP 7 (Debian)…