Backwards incompatible change to Constructs.filter_by_axis API

[davidhassell]

The API changes described in #130 and #132 imply a change in Constructs.filter_by_axis, namely the existing:

    def filter_by_axis(mode=None, axes*):  # v1.8.8.0

becomes:

    def filter_by_axis(axes, axis_mode='and'):  # v1.8.9.0

The old mode and new axis_mode parameters behave the same.

Potential for existing code to silently break

The existing code

>>> d = c.filter_by_axis('or', 'domainaxis1')  # v1.8.8.0

will behave differently with this change in v1.8.9.0, in that both 'or' and 'domainaxis1'' will now count as *axes arguments , rather than the 'or' being assigned to the old mode parameter.

The way to rewrite this code would be:

>>> d = c.filter_by_axis('domainaxis1', axis_mode='or')  # v1.8.9.0