Optimize location lookup, avoid repeated config reads

[adamcandy]

This caches the false states of 'prefer_english_names', which I expect is what was intended.
Fixes #371 (Geolocation examines config.ini for every new lookup).

[coveralls]

Coverage decreased (-0.2%) to 90.877% when pulling aa02369 on adamcandy:prefer-english-names-optimize into 8e95b96 on jmathai:master.

[jmathai]

This looks good. Can you cherry pick the commits from #370 into this branch so we can combine them into a single PR?

[jmathai]

I wonder if we could just initialize __PREFER_ENGLISH_NAMES__ to False instead of None. I think that would have the same effect.