This ensures correctly formatted relative filenames on
Windows. filepath.Clean uses the system seprator character,
while path.Clean always uses a forward slash.
Thanks to @AlexeyUzhva for noticing.
Fixes#146
The go command on Windows doesn't like long path name. To
work around this, this is the first in a series of changes to
shorten the schema disk path structure in a few places.
Fixes#89
The problem this solves is loading and re-saving a document
that uses an odd file structure (e.g. the main body is
not at word/document.xml). I've seen this occur with spreadsheets
but not with a docx in the wild, however it's fairly simple
to handle in case it occurs.
