fix(template-base): update Travis CI config to best practices

[malept]

• I have read the contribution documentation for this project.
• I agree to follow the code of conduct that this project follows, as appropriate.
• The changes are appropriately documented (if applicable).
• The changes have sufficient test coverage (if applicable).
• The testsuite passes successfully on my local machine (if applicable).

Summarize your changes:

Just things I noticed when I was looking at the Electron Fiddle CI config.

[codecov]

Codecov Report

Merging #1539 into master will not change coverage by %.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1539   +/-   ##
=======================================
  Coverage   74.96%   74.96%           
=======================================
  Files          73       73           
  Lines        2121     2121           
  Branches      399      399           
=======================================
  Hits         1590     1590           
  Misses        407      407           
  Partials      124      124           

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