Run tests sequentially across Firefox versions

This removes the overhead of launching/stopping several Firefox versions
for each test program run.
Fix *visible methods, which failed on access to dead JS objects in FF 15+

Such dead objects appear in FF 15+ when you navigate away from a page
but still hold a reference to an object on the page, like a DOM node,
or an object created in that page's context.
Make the test runner more resilient
Remove run_across_instances() as that functionality was moved to a wrapper for `make test`

Thanks to ysth for the nudge
Update Changes for v0.70
Make ->click() use case-insensitive queries when searching for "input" elements

I don't know how I missed this test failure on 3.0.x all the time. Maybe
it's just exhibited now.
Firefox 3.0.19 inserts an empty <title></title> sequence here
Update changes
Rename test away so testing maybe can complete now
Bump version, add releasedate, regenerate examples