float does not return to current column when called inside a column_box

[mojavelinux]

When the float method is called inside a column box, it only restores the original page number and y, but not the current column. As a result, the ensuing content may be written to the wrong column.

[mojavelinux]

I will submit a PR to resolve this issue.

[mojavelinux]

We might want to consider promoting the current_column instance variable to an accessor. It might also be nice to make the columns readable, but that's not needed for this change.