“std::bad_alloc”: am I using too much memory?

## Behaviour and Step to Reproduce
When I running on 8GB RAM, and 16GB swap, it uses full ram and 10GB swap. but still ~5GB free on the swap. Why It raises std::bad_alloc instead of using the rest of swap

* **Version**: 0.7.0
* **Where did you get MITIE**: Clone latest
* **Platform**: Ubuntu 16.04
* **Compiler**: GNU Make 4.1
