detect buildout and add buildout eggs to sys.path

I am trying to add support for buildout based projects to jedi.

So far this seems to work. But I guess it isn't quite ready to merge yet.

A few questions:
* Can (and should) I use jedi.parser to do the parsing instead of using the ast module?
* Is it okay to write a test directly against _detect_buildout  or should tests be written on a higher abstraction level?

i like the solution for now. Maybe we can make it a little bit more sophisticated later... If you want you can also play with `evaluator.eval_statement()` and use `get_index_types` on the resulting array. (`CompiledObject` contains the string elements in `CompiledObject.obj`)

That's how I would have done it. It would cover a lot more cases, but then again almost nobody is using it like this.