Add standard "custom" rules for banning @expose and throwing non-Error objects.  There isn't currently a good generalization of these rules.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=77452930
[NEW TYPE INFERENCE] Use the coding convention for constants.

Also, don't give a misplaced-const-annotation warning for @final constructors.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=77453128
Switch from org.json to GSON for parsing/outputting JSON.

Some GWT users use an alternate jar for org.json which causes build errors. See https://code.google.com/p/google-web-toolkit/issues/detail?id=8762

Fixes #187
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=77454674
[NEW TYPE INFERENCE] Fix incorrect specializing of union types.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=77462197