declare lodash as a prod dep

[alsotang]

The project used _.once but don't declare lodash as a prod dep.

[coveralls]

Pull Request Test Coverage Report for Build 995463608

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 994771868:	0.0%
Covered Lines:	44
Relevant Lines:	44

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💛 - Coveralls

[papandreou]

Whoopsie, thanks! Will make a new release later when I’m in front of a computer 🤗