Use relative module identifiers

To open doors for Node.js interoperability.

```js
var config = require("../package.json");
var dependencies = Object.keys(config.dependencies || {})
    .concat(Object.keys(config.devDependencies || {}));

var fs = require("fs");
var qfs = require("q-io/fs");
var LineInputStream = require("line-input-stream");
var Require = require("../../v2/mr");

var lines = new LineInputStream(process.stdin);
lines.on("line", function (path) {
    if (path === "transform/transform.js")
        return;
    var packagePath = qfs.relativeFromDirectory(qfs.join(__dirname, ".."), qfs.absolute(path));
    console.log("file", path);
    var text = fs.readFileSync(path, "utf-8");
    text = String(text).replace(/(^|[^\w\$_.])require\s*\(\s*["']([^"']*)["']\s*\)/g, function(_, lead, id) {
        var original = id;
        if (id === "montage") {
            id = "core/core";
        }
        var top = Require.resolve(id, "") === id;
        var external = false;
        if (top) {
            var parts = id.split("/");
            var first = parts[0];
            external = dependencies.indexOf(first) >= 0;
            if (!external) {
                id = qfs.relativeFromFile(packagePath, id);
                if (id.indexOf(".", 0) < 0) {
                    id = "./" + id;
                }
            }
        }
        return lead + "require(" + JSON.stringify(id) + ")";
    });
    fs.writeFileSync(path, text, "utf-8");
});
```