switch to namedtuple for coordinates parameters (**BREAKS API**)

[toppk]

this change makes the api a little bit more consistent. it creates a object (a namedtuple) for coodinates, and replaces all uses of lat/long inside noaa_sdk.noaa with this type.

in addition to api breakage, there was a coordinate truncation done in get_observations() that I moved to points() (and implemented as string formatting).

happy to further explain or correct as needed.

[paulokuong]

@toppk thanks. I'm thinking may be you can overload the methods, making them able to accept both coordinate type and tuple.

[toppk]

which methods? all of them?