Xcode9 and Swift4

Some subtle, yet breaking API changes:

1. checkForFirmwareUpdateAsync now returns string of the latest firmware version
2. Remove DisconnectRequested error. If disconnectAsync is called while a connection is in progress, the connect task will finish with isCancelled

New features added:

1. Adding isMetaBoot property on MBLMetaWear object. You can now "connect" to a MetaBoot board but will only be able to look at device information.
2. Reading mac address by default on connection.
3. Expose advertisementData on MBLMetaWear. Makes it possible to parse custom scan response packets.
4. Exposing sleep mode, you can now put MetaWear devices in a deep sleep "off" state

Improvements:

1. Added persistent configuration example (MBLRestorable) to StarterProject 
2. Sensor fusion can run without magnetometer
3. Handle non 200 HTTP codes from the MetaWear server on DFU
4. Pulling device name from advertisement data, it updates much quicker than the cached name property on the Peripheral object

Experimental features:

1. Added ability to create "anonymous" events. This means you can download data from a board which was configured for logging by some other device.
2. Added string identifiers to registers to assist with 1. above