implement manifest functionality

[ralphtheninja]

At the moment deferred-leveldown looks to see if the underlying store has .approximateSize() and if so, adds a function so it can be deferred. This is only a temporary solution and we would need something more generic that can defer any method.

see

deferred-leveldown/deferred-leveldown.js

Lines 51 to 55 in 5b53018

	if (self._db.approximateSize) {
	self.approximateSize = function () {
	return this._db.approximateSize.apply(this._db, arguments)
	}
	}

and

deferred-leveldown/deferred-leveldown.js

Lines 64 to 71 in 5b53018

	if (typeof self._db.approximateSize === 'function') {
	self.approximateSize = function () {
	this._operations.push({
	method: 'approximateSize',
	args: arguments
	})
	}
	}