Re-add support for getting credentials from gcloud for older versions…

… of gcloud.

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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=86122002

Allows users of PubsubIO to specify which pubsub labels are used to p…

…ropagate record timestamps and record ids.

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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=86030744

Version 0.3.20141216

Dataflow on Windows: fix an issue where the ZIP archive would contain…

… file names with a '\' (backslash) on Windows. Using '/' (slash) is compatible with most platforms.

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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=83623330