Fix passvault on 32-bit systems

The passvault's id is created with math.rand as a native int.
If the vault is created on a 64-bit system, it breaks compatibility
with 32-bit systems.

- Generate vaults with 32-bit ids.
- Update testcode
Merge pull request #19 from grittygrease/32bit-compatible

Fix passvault on 32-bit systems