Dev fixes

Hi,

Here are the fixes I had to apply to Ajenti in order to use it on my ArchLinux box.

* psutil returns process info objects with accessor methods to read process data, not properties, so I had to use method calls instead of property reads
* iptables and loadavg plugins had no support for ArchLinux, so this PR contains simple modifications to make them work for Arch
* I found a couple of bugs in HTTP module after some quick code review, I think the commit is self-explanatory
* and the last thing I had to fix, is usage of `k in dir(object)` checks in binder, which made binder skip objects dynamic attributes, so I could not bind some of my models with virtual attrs accessible with `__getattr__()` only.

I know, there are a lot of things bunched up here, and it makes sense to split them up into several PRs, but after all the fixes are relatively small and simple, mostly one commit per fix, so I thought spawning a PR for each commit has little sense, and after all I'm too lazy to do it =)

Thank you.