"Config" menu isn't shown on Windows

The config menu to input our access token to GitHub account isn't shown.
- Clicking the top-right menu button just showed me developer console.
- Right-clicking the title bar showed me the default window menu (such as "Close", "Maximize")

Related: https://github.com/azu/github-reader/issues/5#issuecomment-108966654

Reproduce the Windows app behavior using the top-right menu button and the title bar, then review the discussion in related issue #5. Trace how the config menu for entering a GitHub access token is exposed on Windows; done means the config menu appears instead of the developer console or default window menu.

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