views should not do elementwise comparisons for equality operators.
they are pairs of iterators and are only equal if their iterators are
equal.
instead, use `equal` for elementwise equality. we update the name of
exactly_equal to perform this operation too.
HARD vs SOFT assertions were never very well defined or supported.
Currently they just imply a level of functionality that isn't present;
it's better to remove them instead of expending the effort at this
point.
