Minor changes to solve the 5 errors from eslint - Issue#12

[woneiros]

Minor changes to solve the 5 errors from eslint when trying to fireb…ase deploy

See issue#12: https://github.com/firebase/assistant-codelab/issues/12

I followed https://github.com/lkaybob suggestions for dealing with the five errors that popped up.

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[woneiros]

I signed it!

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