Issue #18: pin versions

We don't want our build process to rely on stability of remote masters. Hence, I've refactored the build scripts and pinned the latest stable version for each dependency.
At the moment, this code is assumed to run in a 32-bit linux VM. There are a whole host of serious problems if this is run on OSX, or any 64-bit platform.

I currently have this documented a bit in ```vagrant/README.md```. However, it might be useful to explain this in greater details.