Allow vgtBigExplosion in low quality mode
Rationale: We already allow vgtExplosion, which is a smaller version. Without vgtBigExplosion, there is not *any* explosion effect.
# physfs-rs [![Build Status](https://travis-ci.org/PistonDevelopers/physfs-rs.svg?branch=master)](https://travis-ci.org/PistonDevelopers/physfs-rs)
## Rust bindings for PhysFS
This project is built against the Rust nightly and PhysFS 2.0.3
[How to contribute](https://github.com/PistonDevelopers/piston/blob/master/CONTRIBUTING.md)