Enhance testing script for more coverage

[sethlu]

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As addressed from #17, there may be ways for testing both compatibility and various minor functionalities that are infrequently called for execution.

[malept]

Perhaps you should consider adding Travis CI to just run syntax checking (node --check) and code style checking (if you're using a particular style, for example either JSHint, or in the case of electron-packager, standard) for supported Node versions.

[sethlu]

@malept Sounds good! I'll have a try to add Travis CI to assist the testing around JS standard.