Tidy up some cmake files

[dtebbs]

Addresses #46

[AntoineRondelet]

Let's look at #50 first and merge this one after the resolution of the problem with test_prover and libboost.

[dtebbs]

Let's look at #50 first and merge this one after the resolution of the problem with test_prover and libboost.

Yes. Sorry about that. For some reason, I didn't need to link boost_system on my machine (mac difference, maybe), so I didn't include it.
I pushed a slightly different way of specifying the boost_system dependency, but feel free to force-push or replace with your PR if you prefer.

[AntoineRondelet]

I pushed a slightly different way of specifying the boost_system dependency, but feel free to force-push or replace with your PR if you prefer.

Have you pushed on this branch? I can't see any new commits to link boost_system

[dtebbs]

Sorry, the push didn't work. Should be there now.