Microsoft Mobile Center added (#52)

* Micorsoft Mobile Center added
* Mobile Center added as dependency in podspec
* Updated Readme with new provider
* updates travis to build with Xcode 9.1

More updates for Swift 3 (changed NSError to Error and NSURL to URL)

attempting to fix Localytics podspec by updating Localytics pod

updated Adjust version

Updated podspec version number to 1.2.7

removed TestFlight subspec

added support for disabling NewRelic features

bumped Adjust.io version, bumped to 1.2.3

bumped to 1.2.3

bumped version to 1.2.2