Multiprocessing not working yet

[bliepp]

Multiprocessing is not working because different processes cannot write to the same TextIOWrapper (aka. file stream). A solution could be to use a queue to buffer the items and leave the writing load on a single process.

Keep in mind that multiprocessing in general will screw up the order of the lines in the exported file. For the atoms this isn't a big deal but the comments should stay in the same order.