Run Travis builds on Node 10.0.0

[NMinhNguyen]

What: Ensure we actually run builds against the lowest version of Node that we support

Why: Node 10.0.0 is our lowest version of support

How: Be specific about the version of Node in travis.yml - specifying just 10 pulls down the latest Node 10

Checklist:

• Documentation added to the
  docs site
• I've prepared a PR for types targeting
  DefinitelyTyped
• Tests
• Ready to be merged
  

[codesandbox-ci]

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Latest deployment of this branch, based on commit 308ca67:

Sandbox	Source
intelligent-mayer-lud78	Configuration

[codecov]

Codecov Report

Merging #467 into beta will not change coverage.
The diff coverage is n/a.

@@         Coverage Diff         @@
##           beta   #467   +/-   ##
===================================
  Coverage   100%   100%           
===================================
  Files        22     22           
  Lines       420    420           
  Branches    100    100           
===================================
  Hits        420    420

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[kentcdodds]

Thank you!