Include inactive memory in mac/linux available.

[dbwiddis]

Closes #23.

[dblock]

Make this something that looks like the line above:

[#25](https://github.com/dblock/oshi/pull/25): Include inactive memory amount in GlobalMemory#getAvailable on Mac/LLinux - [ ... ]

You can commit with --amend and force push up to avoid having to re-squash things.

[dbwiddis]

Unfortunately I didn't have the pull request # until I committed (I suppose I could have guessed). And since I've been committing via svn, I am really unfamiliar with the git command lines to do this. Argh. I'll do my best, I guess... you're really making me have to learn new tools!

[dblock]

It's an opportunity!

We force this strange construction where you commit, then push, then make a pull request, then amend. It's weird, but it's the best we have for changelog entries that seems to make the customer (the developer reading the changelog) happy.

[dbwiddis]

Well, that was painful, until I figured out to use the -f switch on my push... I think this is finally all set.

[dblock]

It may be hard, but is there a way to write a test here that would have failed without the code change? Try something?

[dbwiddis]

For testing, we can try to parse other memory commands.

• on Linux the code draws from /proc/meminfo. We could parse the output from "free -m" instead and look at the "free" column. The old version matches the first "Mem:" line, the fixed version would match the second "-/+ buffers/cache"" line. (We could also pull info from vmstat or top.)
• on Mac the code draws from vm_stat. We can pull from top (top -l 1 | grep PhysMem) to find the old, incorrect value. I don't know if there's any other command line version to get the new version, but it's available on system information display.
  Unforunately, for both tests, there's no way to guarantee that a system will have nomzero inactive memory. Right after reboot, the numbers may be similar/equal.

[dblock]

Merged, looking forward to more!