[#8] Added logos and packager scripts for packaging the app

[dylanfu]

Resolves #8.

A logo for VisualGit already existed. However, on Mac the app showed as an electron logo even when it was packaged for release (See #8 ).

• Added .icns, .ico logo formats.
• Added package scripts with the --icon option for each OS in package.json.

To manually test:

• Remove all previous compilations and packages.
• npm run compile this should generate the required .js files under out/
• npm run package-mac this should generate a package under releases/.
• Run the VisualGit.app, and check it runs as expected with the VisualGit logo.

• To test the packaging on windows or linux use npm run package-winor npm run package-linux respectively then run the application.

NOTE:

• A .png logo is referenced in main.js, therefore the VisualGit logo won't appear in development using 'npm start' on Mac. Which is overrided by the --icon option when packaging the app.
• Also removed index.js, as it is not referenced anywhere in the codebase (Was replaced by main.js).

[Excaleo]

Nice removal of index.js. How long should packaging take? Packaging on windows seems to hang.

[dylanfu]

@Excale0 usually takes a few minutes.

[dylanfu]

@sloushsu I've removed the build folder, bash scripts, and the outdated README.pdf. Ready to merge.