namespace option rewriting internal require calls

[jrburke]

For namespace: 'foo', This:

define(function(require) {
    var a = require('./a');
});

should not be converted to:

foo.define(function(require) {
    var a = foo.require('./a');
});

but instead should be transformed to:

foo.define(function(require) {
    var a = require('./a');
});

Otherwise, local require calls will not get resolved correctly.

[jrburke]

The builds.js test buildNamespace actually shows this problem. So fixing it so that modules/three does not have its internal require calls rewritten will be a good test case to verify the fix for this issue.