new narrative style use case added to wiki

Hi - I've added a new climate data use case<https://www.w3.org/2013/csvw/wiki/Use_Cases#Creation_of_consolidated_global_land_surface_temperature_climate_databank> to the wiki page. It illustrates the real things that people are trying to do with CSV data (well, delimited tabular text files, not proper CSV). I'd appreciate feedback on the style; my initial thoughts are that it might be a bit long - but it's difficult to see how to shorten it without removing the narrative context. Perhaps I think people will be interested in stuff that is irrelevant for the CSVW context?

I've included some initial REQuirements ... but we'll need to work though all the use cases to pull out a consistent set.

I'll add this to the use case document<http://w3c.github.io/csvw/use-cases-and-requirements> then get on to working through other's use cases.

Jeremy