leading and trailing space in element name

Hi,
I've got a schema with a trailing space in an element name, this is valid XSD, so when I test a round trip marshaling on it, it throws an error when marshaling back in the function writeStartElement when executing :

``` javascript
element = this.document.createElementNS(namespaceURI, qualifiedName);
```

because `qualifiedName` ends with a space.
According to the [XSD spec](http://www.w3.org/TR/2004/REC-xml11-20040204/#AVNormalize) :

> If the attribute type is not CDATA, then the XML processor MUST further process the normalized attribute value by discarding any leading and trailing space (#x20) characters, and by replacing sequences of space (#x20) characters by a single space (#x20) character.

I think it is the role of the schema compiler to trim the attribute name. So the mapping file would contain the trimmed names. But maybe a trim in the js part would be useful too.

Thanks for your great work on this library.