Replace hhvm to hhvm-3.30 on Travis
Replace hhvm to hhvm-3.30 on Travis

Composer is not support hhvm any more, thus,
composer cause error in hhvm-4.x.
hhvm-3.30 is the last php support version as
https://hhvm.com/blog/2018/12/17/hhvm-3.30.html

butane/CodeIgniter,Bluewind/filebin,butane/CodeIgniter,Bluewind/filebin,butane/CodeIgniter,Bluewind/filebin,madwings/InsaneDB,madwings/InsaneDB,madwings/InsaneDB,butane/CodeIgniter,bcit-ci/CodeIgniter,madwings/InsaneDB,butane/CodeIgniter,Bluewind/filebin,bcit-ci/CodeIgniter,bcit-ci/CodeIgniter,bcit-ci/CodeIgniter,Bluewind/filebin,madwings/InsaneDB,bcit-ci/CodeIgniter