Fix the UnexpectedEOF in the source

[eudoxos]

The page https://github.com/pearu/pyvtk/wiki/unexpectedEOF suggests a way to fix UnexpectedEOF on files which are conforming to the ambiguous standard for VTK2. 3rd-party projects using pyvtk have to monkey-patch pyvtk to open such files (see https://sourceforge.net/p/mupif/code/ci/master/tree/mupif/VtkReader2.py at the end of the file for a case in point).

This workaround should be either optionally enabled in pyvtk (without monkey-patching), or better yet (as it is safe as far as reading valid input is concerned) change the split(' ') to split() for good so that both variants are readable.