Store/retrieve tab with location hash

For a project I'm working on it was necessary for the current tab to persist after creating/updating an entry.

I made a few modifications to parenthesistabs.publish.js to allow this to happen, storing and retrieving a reference to the current tab using the location hash. A secondary benefit is that a given tab can be linked to directly, which I imagine could be useful in some cases.

I'm not entirely sure whether it makes sense for this to be the default behaviour of tabs, but I thought I'd create a pull request so you can take a look and decide for yourself!