formatting tweaks to CHANGES
Flesh out README
gitignore vim swap files
Guarantee that all of the required entropy is read on Unix
stop build on errors
bump to 0.1.5
Add a `Entropy_xen_weak` module.

This uses the builtin `Random.self_init` as a measure of last-resort.
It can be enhanced later to check for interrupt timings and such.
remove Entropy_xen_weak and fold it into Entropy_xen

After discussion with @pqwy, there's no point in
distinguishing these noise sources.  We should instead
hook in a solid PRNG like Fortuna before the consumers
ever use entropy.
Merge pull request #2 from avsm/master

Packaging tweaks + ensure complete entropy request is fulfilled