Added support for ASCII VTK fiber sets.

They are automatically converted to a temporary binary VTK file, which is easier to parse.

Also fixed a few minor typos, and added an explicit close() to the input file in Tractconverter.py.
Merge pull request #3 from jchoude/Fix_Ascii_VTK_Reading

Added support for ASCII VTK fiber sets.
Merge branch 'master' into unittest