Update names.py

[bjtho08]

Added metric names 'categorical_accuracy', 'val_categorical_accuracy', to support categorical metrics.

[coveralls]

Pull Request Test Coverage Report for Build 482

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.2%) to 85.243%

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Totals
Change from base Build 481:	0.2%
Covered Lines:	1086
Relevant Lines:	1274

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💛 - Coveralls