Refactor common elements from modules into a common module

[ryankurte]

Some common identifiers and types are sneaking in across modules, probably time to have a look at what can be refactored out and shared across modules to avoid redefinitions.

[thearavind]

Can we create a separate package for the types and import them and reuse it in all other modules, Will this work???

[ryankurte]

Possibly yep, but it only makes sense to extract types that are shared between modules I think.
It's also kinda neat that each module has all the required types internally, and extracting them might make usage less clear :-/

import (
    "gopkg.in/ryankurte/go-mapbox.v0/lib/maps"
)

img, err := mapBox.Maps.GetTiles(maps.MapIDSatellite, 1, 0, 0, maps.MapFormatJpg90, true)

Could end up being:

import (
    "gopkg.in/ryankurte/go-mapbox.v0/lib/common"
    "gopkg.in/ryankurte/go-mapbox.v0/lib/maps"
)

img, err := mapBox.Maps.GetTiles(common.MapIDSatellite, 1, 0, 0, common.MapFormatJpg90, true)

So maybe this needs some more thinking about.