add smtp config

[JuanVqz]

• Add letter_opener gem
• Add production smtp config
• Add mailer views and improve es locals

[codeclimate[bot]]

Code Climate has analyzed commit 035901d8 and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 100.0% (50% is the threshold).

This pull request will bring the total coverage in the repository to 94.7% (0.0% change).

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