A few improvements

[SmartFinn]

The PR adds a few changes that I using in my private fork of this project:

1. Avoid using GitHub API calls to allow more than 60 request per hour per routable IP
2. Reduce execution of external commands when it possible
3. Fixes regex in sed to avoid false matching
4. Add short forms for options
5. sdd list shows installed packages if no extra option specified

[pylipp]

Thanks a lot! This brings many usability and code readability improvements.
I noticed one failing test, do you mind having a look why? EDIT: not related to your changes, I'll have a look myself :)
You can also extend the Changelog (mention the new short option forms, and the fix) and update the README (section about listing apps).

[SmartFinn]

@pylipp the changelog updated. In relation to README, I have no idea how to mention the short options except duplicating the commands.

[pylipp]

Thanks again for the contribution! How did you find the project, and what are you using it for?

[SmartFinn]

I saw your post on Reddit and I thought that is a good way to replace my zsh functions for installing binaries from GitHub to the separate app.