Make log level for GWT configurable for Maven builds.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=79283169
Make GWT less spammy for Travis CI builds by changing its log level to INFO.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=79291520