Response files without under/overflow

[israelmcmc]

In histpy 2.0 we no longer need to keep track of the underflow and overflow bin, and it performs much better when we don't.

However, if the contents are initialized including the under/overflow bins, they are not dropped by default. Our current responses do include these bins, so even if we start using histpy 2.0, we won't see all its benefits until we update the response files as well.

Pointed out by @jdbuhler