(#2415) - add LEVEL_PREFIX option for riakdown etc.

[nolanlawson]

Forgot to add this for riakdown etc. Gonna open this up for testing, though, so we can validate that it actually works for *DOWN authors.

[nolanlawson]

Oh yeah, and read this guide to see why I need this option.

[nolanlawson]

All right, as @nlf pointed out to me, this test was actually pretty broken for the LEVEL_PREFIX. In fixing it, I discovered some more issues with my implementation of PouchDB.defaults. It was tricky enough that I added a test to make sure that we can successfully complete when using leveldown plus an arbitrary LEVEL_PREFIX.

On the bright side, I discovered that the errors with MemDOWN were our own, so it looks like now we can remove memdown vs. memdown from the allowed failures.

[nolanlawson]

Sorry for the churn on the following three tests. All I did was wrap them in an if statement to skip them if we're using any settings other than just the default leveldown with no prefix.

[nolanlawson]

Got confirmation from @nlf that RiakDOWN now passes the test suite as both the client and the server. :)

[nolanlawson]

Tested sqlDOWN and the tests passed with it on the server and the client. Had to npm link pouchdb-server to this branch of pouchdb in order for it to work, but it works!

[calvinmetcalf]

var createOpts = utils.extend(true, {}, opts, {adapter : backend.adapter});

[nolanlawson]

nice, thanks

[nolanlawson]

All the recent PRs are failing in Travis for the ADAPTERS browser tests, with the error No valid adapter found. Looks to be an error in one of our dependencies. This is why I hate caret and tilde versioning.

[calvinmetcalf]

link to a failing build?

[nolanlawson]

NM, s'all good now.

[nolanlawson]

rebased

[nolanlawson]

Fixed unnecessary utils.clone()

[calvinmetcalf]

👍

[nolanlawson]

d8ee227