(fix) don't provide auth option to nodemailer when no username and password is provided, fixes use of SMTP servers without auth

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Release 0.2.6

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chore(grunt): set up release process

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chore(travis): initial setup

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docs(readme): add dependency badges

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chore(travis): run integration-test on ci

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chore: migrate to grunt-release-hoodie v2 and new GH_TOKEN

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chore(travis): enable sudo queue and cache

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Merge remote-tracking branch 'upstream/master'