`show_doc` rendering issues with TorchScript functions

`show_doc` currently has rendering issues with TorchScript functions.

```python
import torch
from nbdev.showdoc import *

@torch.jit.script
def test(p:torch.Tensor):
"Test torchscript function"
return p

show_doc(test)
```
results in the following output, without a source link in the documentation
```
## ScriptFunction object at 0x7fc550c680e0>
Test torchscript function
```
switching to `show_doc(test.name)`, where `name` is a torchscript function property, displays the method name and github source code link, but not the docstring:
```
## test
test
```