improved on script with aria2c

[albertfougy]

#92 and #88 issues are squashed with the aria2c tool.

[philipmat]

That looks pretty awesome (also yay VSCode!)

Can we make it so that if the computer doesn't have aria2c installed, we fall back on wget?

[albertfougy]

w/ conditional provided client does not have aria2c installed.

w/ wget exclusive of aria2c

Besides adding the "fallback" conditional for wget.

1. refactored deprecated string interpolation
2. added shebang
3. split long statements in a couple of places
4. added another flag for wget to show progress from left to right

[philipmat]

Thank you very much for making the code more readable.