Session06 Pull Request

Task 1 - HTML Rendering
consider simplifying this by assembling the attributes into an intermediate string:

```python
attrib = "".join([' {}="{}"'.format(k,v) for k, v in self.attributes.items()])
file_out.write(u"{}<{}{}>".format(indent, self.tag, attrib))
```
It's a bit cleaner and clearer what is happening.