[FIX] allow to also use standard mzML instead of indexedmzML for the Writer
[FIX] allow to also use standard mzML instead of indexedmzML for the Writer

The mzML root node needs to be added to the TreeBuilder otherwise the
child elements are added without a root!.

pymzml/pymzML,StSchulze/pymzML,pymzml/pymzML,StSchulze/pymzML