FCM Migration

Merge pull request #9 from johneg1/master

Updates readme and build dependencies

release/1.1.8

Merge pull request #4 from websms-com/dev-additional-methods

release/1.1.7: Merge pull request #5 from websms-com/dev-concatref

handle multipart messages

release/1.1.6

~ store attachment id when failover message is updated

release/1.1.5

~ strip country code for address comparison

release/1.1.4

~ add message priority