Fix migration of very-old etherpads.

I don't know why ueberDB's name changed.

The commit message does not explain it:

ether/ueberDB@423e40f

There is this tweet, and the tweets chronologically after it, but they just complain vaguely of an "npm issue" without explaining the issue:

https://twitter.com/johnmclear/status/683454253856337920

Fixes #29

src/sandstorm-migrate.js

@@ -9,8 +9,8 @@
 // place. But we need to migrate old pads. So that's where this script comes
 // in.
 
-var ueberDB = require("ueberDB");
-var dirtyDB = require("ueberDB/node_modules/dirty");
+var ueberDB = require("ueberdb2");
+var dirtyDB = require("ueberdb2/node_modules/dirty");
 
 var dirty = new dirtyDB("var/dirty.db");
 var sqlite = new ueberDB.database("sqlite", {filename: "var/sqlite3.db"});