[4078] Szablony (jinja2).

https://gist.github.com/lukkolstx/4046bcbc73f4a2cfe02d
Fixed. Please review.
ok this is good, but... 
```python
@app.route('/<template_name>', methods=['GET'])
def render_templates(template_name):
    ...
    template_name = "{}.html".format(template_name)
```
would be better