Refactor to add config watching and test coverage

[dcalhoun]

Includes a significant refactor to accomplish the following.

• Improve test coverage.
• Add config watching (i.e. remove need to restart Hyper after updating hyper.js config).
• Utilize Hyper’s set of windows rather than managing a duplicate set within the plugin.
• Change default setting for hideOnBlur as it was confusing users.
• Properly remove event handlers during plugin uninstallation.
• Add StandardJS linter to avoid syntax errors.

Jest Coverage Report

------------|----------|----------|----------|----------|----------------|
File        |  % Stmts | % Branch |  % Funcs |  % Lines |Uncovered Lines |
------------|----------|----------|----------|----------|----------------|
All files   |    96.43 |    86.36 |    94.12 |    97.96 |                |
 app.js     |    94.44 |      100 |       80 |      100 |                |
 dispose.js |      100 |      100 |      100 |      100 |                |
 toggle.js  |      100 |      100 |      100 |      100 |                |
 windows.js |    96.55 |    81.25 |      100 |    96.15 |             49 |
------------|----------|----------|----------|----------|----------------|