This brings the library up to date for Xcode 10 and Swift 4.2

Release 3.0 - Updated the source code and project to function correctly without deprecations and warnings in Xcode 9 / Swift 4.

Release 2.0 - New features, API renaming and project restructure.

• Added bounding box methods for shrinking, detecting if a coordinate is within a bounding box
• Adjusted APIs to be consistent with one another and use Core Location typealiases where relevant
• Fixed a bug when calculating the bearing
• New midpoint variable on BoundingBox and extension on CLLocationCoordinate2D to calculate midpoint between sender and receiver
• Initial SPM support

Support for macOS, watchOS and tvOS formalised in the project.