Minor online docs remarks

[adeak]

I suspect the online docs are very much being developed dynamically, but anyway I ran into two minor things at a first glance:

1. There's no link from the documentation to the github repo (at least I couldn't find one and neither could the internal search box). The github.io URL makes this half-obvious, but there will probably be users who would open issues but don't know where to look.
2. In the threading section the figure has a few red squiggles from a spellchecker: np.add, arange, rnd (is rnd a pnumpy thing? I couldn't find it in numpy.)