import .eslintrc from Haraka, lint fixes

[msimerson]

• import .eslintrc from Haraka
• fix lint issues
• remove node 0.10 testing
• remove node 5.0 testing
• add node 6.0 (LTS) testing

[codecov-io]

Current coverage is 87.57% (diff: 100%)

No coverage report found for master at ce1ea83.

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