Update documentation - curl should be more robust on redirects

Hi,

curl should be configured to follow redirects and within builds it should also be as silent as possible. I'd therefore propose to update the documentation slightly.

The related changes / missing parameters cause problems which are quite hard to debug (see builds 28,29,30 in https://travis-ci.org/tolleiv/repoactivity/builds)

Besides that - thanks for providing these great scripts.
Cheers, Tolleiv