No problem; the only reason I sent an email was that we had been doing that before, and I wasn't sure if you had notifications set up.
I've followed the guide, but when I tried running my scraper, I got the error
Could not find rake-12.0.0 in any of the sources
From looking on the internet, it seems that this problem is indicative of a version mismatch somewhere in the system.
I confirmed that there is indeed a problem with the way I've set rbenv up, because if (as suggested in this link) I type
$ rbenv install 2.2.4
$ rbenv global 2.2.4
$ ruby -v
I get the output
ruby 2.3.3p222 (2016-11-21) [arm-linux-gnueabihf]
Which implies that the version isn't changing.
I installed rbenv using apt-get - perhaps I need to compile it locally?