[#45] Add AppVeyor to hs-init

[chshersh]

Resolves #45

I've added AppVeyor as a separate CLI flag. Maybe if --ci specifed we can add both Travis and AppVeyor. I'm not sure what is more convenient for users. Maybe somebody don't want to deal with Windows...

I've also performed some cosmetic changes. And added appveyor.yml to hs-init.
@vrom911 you probably need to add hs-init project to AppVeyor to launch builds. I don't know how chmod +x works on Windows and how can I launch hs-init --help on Windows so I just build it with ghc on Windows.

Here is the example of project I've created to test AppVeyor:

• https://github.com/ChShersh/appveyor-test2

[vrom911]

I'm very happy with this changes! Looks great, thank for this very useful feature!
I've added hs-init at appveyor but it unfortunately fails for some reasons. It couldn't find any of the packages specified in the stack script. I remember specifying them in travis.yml before, probably something like this should be done in appveyor file.
https://github.com/vrom911/hs-init/blob/2d6ccbe336fe1dc4438d8ddbfeb835280ca316f8/.travis.yml#L25

[vrom911]

Here it names the version twice: it the label and in the link, so the first one should be 1.0.3 also.
Yes, I know that it's not the best way to keep version updated, but I don't know to deal with it..

[chshersh]

No problems 👌 I also don't know better way...

[vrom911]

Oh, sorry! I thought I merged it loooong ago!
Thanks for these changes, that's awesome 🥇