Adding test for stl container of vex::vectors
Adding test for stl container of vex::vectors

Doesn't seem to trigger the problem mentioned in #25.

ddemidov/vexcl,ddemidov/vexcl,kapadia/vexcl,Poulpy21/vexcl,kapadia/vexcl,Poulpy21/vexcl,Poulpy21/vexcl