Update xlrd/compdoc.py

fixed AttributeError: 'DirNode' object has no attribute 'totsize'
Initial changes for Python 3 compatibility.
Remove extraneous print from demo code.
Use truediv instead of floordiv in formula.
Add tests from xlrd3

https://bitbucket.org/mozman/xlrd3
Tweaks to tests.
Add script to run tests.
Include changes to formula parsing from xlrd3

https://bitbucket.org/mozman/xlrd3/changeset/84447954d33f
Correction to tests for Python 2.
Use unicode in tests with Python 2.
Add trove classifiers for Python 2 and 3 compatibility.
Some more fixes for bytes literals
More use of byte_0 and bytes_empty.
bytes fixes in hex_char_dump()
Use get_int_1byte in more places.
b() -> BYTES_LITERAL()
Remove non-corresponding xfcell tests.
Update tests to new package structure.
Use sjmachin's Python 3 compatibility functions.
Fix relative imports