Allow adding/deleting IPs using CIDR notation

Note that this interacts weirdly with the existing range support.
Please avoid using both features on the same line.
Fix import by enumerating as objects

Previous commit didn't actually work.
Explain input format on batch add/delete page

This should make it clearer what we're looking for.

Spacing is a little funny, could maybe use some CSS love.
note CIDR support in README
Merge pull request #10 from peter-mtso/cidr

Add CIDR support to bulk add/delete