Add failing test for #44

[Victorystick]

Test tokenization of this snippet:

```c
int deref(int *ptr) { return i*; }
```

Rendered:

int deref(int *ptr) { return i*; }

In Atom, both the int and return keywords fail to be highlighted. Not to mention the italics.

I cannot figure out why any GFM rule (other than the terminating ```) should apply inside the code block.

[50Wliu]

Yes, this is a bad bug that I've wanted to investigate for some time now. It might have to do with the fact that language-c didn't tokenize operators like * until just 14 days ago. I wonder if this will be fixed when that change reaches stable and language-gfm picks it up.