Support for context, plus code address

[mariotoffia]

Hi and thanks for a nice framework. I've forked it and did a minor update to at least return city, country (and added GlobalCode) in google lookups.

Also added context to the api calls since I use those in lambdas and need to cancel when lambda timeout. I also need the context in the logger (extracts certain values from context when logging).

I've done this in the following fork: https://github.com/mariotoffia/geo-golang - if it is ok - I can create a pr (of which I revert back my renaming of package to yours).

Again, many thanks!

Cheers,
Mario :)

[codingsince1985]

yes please @mariotoffia