Allow the user to call tight_layout
Allow the user to call tight_layout

The use of `set_visible(False)` breaks the `tight_layout()` routine and
produces a AttributeError when it is called.  This replaces the
`set_visible` call by removing the ticks manually and, since there is
now no need to force the `tight_layout` to be False, also removes the
occurances of this.

allisony/triangle.py,sedonaprice/corner.py,lisaleemcb/triangle.py,dfm/corner.py,philrosenfield/triangle.py