Rename MapboxGeocoder.swift to Mapbox Geocoder for Swift

This project was originally named MapboxGeocoder.swift because it started as a single file named MapboxGeocoder.swift in 2c2a827283d03fbd075719b7d158066084a3442a. (Lore has it that, even before this repository existed, it was a gist by the same name.) Over the years, the “dot swift” extension has been a bit of a mouthful and even occasionally a source of build issues: https://github.com/mapbox/MapboxGeocoder.swift/issues/59#issuecomment-327346187. Having “.swift” in the name also causes confusion because the library also supports Objective-C. Emphasizing Swift in contrast to Objective-C matters less and less these days in Apple-centric environments like CocoaPods.

As we’re doing with MapboxDirections.swift in mapbox/mapbox-directions-swift#399, I think we should consider renaming the project to “Mapbox Geocoder for Swift”, the repository to mapbox/mapbox-geocoder-swift, and the pod to simply “MapboxGeocoder”. Any developer installing the library using CocoaPods would need to replace `MapboxGeocoder.swift` with `MapboxGeocoder` in their Podfile. Otherwise, there’s no immediate impact to developers, since GitHub automatically redirects renamed repositories.

Ideally, this change would take place as part of a v1.0 release that also drops Objective-C compatibility. However, there aren’t active plans for either at the moment, so this issue is just a placeholder for now.

The steps to rename look roughly like this:

* [ ] Replace occurrences of “MapboxGeocoder.swift” in the repository
* [ ] Rename the repository to mapbox/mapbox-geocoder-swift
* [ ] Update Bitrise configuration
* [ ] Update CircleCI configuration
* [ ] Update Codecov configuration
* [ ] Publish v1.0 (and any prereleases) to a new “MapboxGeocoder” pod
* [ ] Deprecate the MapboxGeocoder.swift pod in favor of the MapboxGeocoder pod
* [ ] Update documentation across docs.mapbox.com

/cc @mapbox/ios

Start by searching the repository for “MapboxGeocoder.swift” and reviewing the Bitrise, CircleCI, and Codecov configurations, Podfile references, and documentation links. Confirm the repository, pod, and project naming changes before coordinating the v1.0 release and deprecation plan. Done means the checklist is complete, including docs.mapbox.com updates and migration guidance for CocoaPods users.

Written by the indexing model from the issue text.