Update upgrade guide

[ralphtheninja]

We need to rewrite the upgrade guide for the currently unreleased functionality, since test/common is now both for node and the browser (empty setUp() and tearDown()).

• [x] Implementations need to create their own factory and pass in testCommon
• [x] testCommon parameter no longer has default value (NYI)
• [x] seek
• [x] test/common is a function (NYI)
• [x] removed deprecated module.exports.snapshot test (NYI)
• [x] removed empty errorValues test (NYI)
• [x] Refactored chained batch (pending #257)
• [x] Removed testCommon.collectEntries
• [x] test/close-test.js updated with setUp and tearDown (https://github.com/Level/abstract-leveldown/pull/279)
• [x] Serialization (pending #277)
• [x] Remove "Empty errorValues() test was removed"

See discussion in #258

[ralphtheninja]

So some of these are no longer relevant, given that test/common will be removed.

[vweevers]

Can skip "removed deprecated module.exports.snapshot test" because that hasn't been released yet.

[ralphtheninja]

Same for errorValues test. Only seek stuff left for now.

[vweevers]

Ticked off the rest of the boxes to see what's done. Added chained batch + collectEntries.

[ralphtheninja]

Added note on test/close-test.js

[vweevers]

That's another internal detail, no?

[ralphtheninja]

That's another internal detail, no?

True. I was just thinking that some implementations are currently calling .close(). Maybe explaining about a single test function is enough?

[vweevers]

All implementations should no longer require() the individual tests, so we don't have to explain changes we make to those internals :)

[vweevers]

Added a task for #277.

[vweevers]

Added: Remove "Empty errorValues() test was removed" ;)