1.1.0 Release

Updated Android compileSdkVersion to 28

Please make sure to update to compileSdkVersion 28 in your build.gradle when updating to this version or newer!

• compileSdkVersion at version 28 is now the default the latest Flutter version
  • Fixes build time error Execution failed for task ':onesignal:verifyReleaseResources'.
  • Issue #61