Since 0.13 is released successfully, it's good time to remove classes deprecated.
We can remove the followings safely.
But, we can not delete the following although this is deprecated since 0.13.
- wake/storage/StorageIdentifier.java (FileIdentifier implements StorageIdentifier)
If nobody use `FileIdentifier`, we can mark `FileIdentifier` as deprecated since 0.14, too. REEF 0.15 will remove both files and wake/storage/package-info.java.