Make possible to change < and > (the tags' delimiters) by two other chars

Consider the following python example taken from the official documentation:

```python
>>> fib

```

If we want to execute this we need to remove the memory address as this is likely to change from one run to another.

Using ``<...>`` is the correct solution *but*, the expected string is already using ``<`` and ``>`` so we cannot distinguish a literal ``<`` from the begin of a tag.

We need some way to change the delimiters, something like:
```python
>>> fib # byexample: +tags=()

```