(#1767) - get memdown attachments working in browser

[nolanlawson]

No description provided.

[nolanlawson]

The attachment tests pass if you marry this PR with Level/levelup#246. The only tests that don't pass are

• sync (apparently @adamshih is already on this)
• migrations (because they don't make sense for memdown; I'll fix them in a later commit)

Other than that, MemDOWN is green as hell in the browser (Chrome).

[nolanlawson]

Also this code is terrible, hence WIP. But I will fix in a bit.

[nolanlawson]

OK, ready. Although the code might still need a refactor; some things are weird (e.g. why the 'md5-' prefix only in the browser?).

[nolanlawson]

I'm not sure why memdown is working but level-js and localstorage-down are not. Feel free to run the attachments tests; something is slightly off.

[nolanlawson]

Yay, memdown attachments are green in Safari and Firefox too. Improbable!

[calvinmetcalf]

memdown doesn't serialize anything so less to break

[daleharvey]

e9feb99

@nolanlawson if you have memdown green its probably worth adding to travis, these fixes helped localstorage in chrome, but still broken in firefox

[nolanlawson]

Yeah sorry, it's the migration tests that are remaining. It's really just a matter of ignoring those tests unless we're in IDB.

Speaking of which, if we add localStorage to the official release, I guess we'll also want a localStorage -> IDB migration.