Fixes #209.

_checkShape now considers also dtype.shape when checking if
array broadcasting is necessary.

Removed raising ValueError exception because redundant: the
same exception is raised by the numpy broadcast.
Add a test case for issue #209
Rewrite BroadcastTest to a simpler and pep8 compilant version.
Merge branch 'issue209' of github.com:andreabedini/PyTables into andreabedini-issue209