Tests! Fix #15

Fix #15 (closed), read and write aren't as dumb now. I removed locks for Linux read/write, because I'm not sure how to accomplish that locking on other platforms. Idk if std has a way to do it. Also, I should have used #[cfg(not(redox))], so that's something to fix.

Tests are in! Doctests work, they all pass, as do the five that I wrote for that specific purpose. The doctests look good in the docs too.

I'm going to release this version of the crate on crates.io. I hope no one has any objections.