 Completely rebrand Cirodown to OurBigBook

The name cirodown should not appear anywhere now, except with very few exceptions, e.g.:

I have also squatted OurBigBook on all major social media handles for near future usage, e.g.: twitter.com/ourbigbook and so on.

I was going to do this sooner or later, it was inevitable, but the timing was partly triggered due to noticing that English speakers (and likely many other nationalities) are not able to easily read/hear/pronounce "Ciro".