Bugscrub

Wrote a few more tests, basically covering everything that I do when I run the client manually to check for problems.

I fixed a handful of things. For the most part, after this Sia should be ready for alpha v2. We can probably switch over to the release branch and start optimizing that.
this is unsafe if `len(downloadBytes) > len(randomBytes)`. Unlikely, but possible. Just use `bytes.Compare()` unless it's really valuable to know which byte is different.