Support for SVG

Might be nice to have as well. Made a start:

```python
import io
import base64
from IPython.display import display, HTML

plt.scatter([1,2,3], [54,12,2])
plt.title('this is a demo')

my_stringIObytes = io.BytesIO()
plt.savefig(my_stringIObytes, format='svg')
my_stringIObytes.seek(0)
HTML(my_stringIObytes.read().decode())
```