2.0.0 Release

Added

• Nexmo Voice API
• Automated testing and code quality with Travis CI, Codecov and Codacy
• Publishing to Maven Central
• Complete refactoring and reorganisation of the library. All classes are now
  under the com.nexmo.client package.

Changed

• New Insight API using non-deprecated endpoints.
• Migrate to Gradle
• Internal refactoring for unit testing
• Removed example code. See nexmo-community/nexmo-java-quickstart instead.