fix ci by moving to containerized build
fix ci by moving to containerized build

The legacy builds have a buggy bundler. Also remove rbx (which was crashing) and add ruby 2.3.

bobbrez/cequel,orenmazor/cequel,visfleet/cequel,shaqonline/cequel,orenmazor/cequel,bobbrez/cequel,jhannus/cequel,shaqonline/cequel,devnut/cequel,jhannus/cequel,cequel/cequel,devnut/cequel,visfleet/cequel,cequel/cequel