Maven Central requires fixed dependency version numbers

Updating to use latest AndroidAsync v1.4.1

Invalid POM: /com/simperium/android/simperium/0.6.1/simperium-0.6.1.pom: Invalid version for Dependency {groupId=com.koushikdutta.async, artifactId=androidasync, version=1.+, type=jar} - uses invalid dynamic version syntax. Replace with a fixed version or standard mathematical notation e.g., [1.5,) for version 1.5 and higher.