[Feature request] Linux support #77

Having support for Linux would be useful to parse results on a separate machine.

I've tried using Xcparse on Ubuntu, almost everything seems to build fine except for some missing imports and the missing support for UTTypeConformsTo. You can find a WIP commit in my fork which builds, but I had to comment out some of the attachment filters: endanke@85c31b3

I wonder if it would be possible to replace that function with a custom implementation? I haven't tested the rest of the functionality otherwise, but it's a good sign that it's building with only slight changes.