Switch from cargo-generate to kickstart

[jonas-schievink]

kickstart is vastly simpler and easier to predict. It shouldn't run into the unreproducible CI errors in #46.

Drawbacks:

• Author is no longer automatically filled in from git
• We have to ask for both the package name and the crate name, because kickstart does not automatically give you both

[Sympatron]

This was already discussed in #36 and implemented in #38.

[sassman]

I will created ci integration test on cargo-generate, very unfortunate that you run into those issues.

I hope we can prevent that in the future.

[jonas-schievink]

@Sympatron oh, somehow I missed that PR, will take a look later.

@sassman Thanks! It's great to see cargo-generate maintained again.