Minor improvements

[0x5ECF4ULT]

I started a fork about a week ago and made minor improvements. Most notably:

• made it clear what kind of cert this is on first sight #11
• made expired certs "phase out" (basically I tweaked the alpha value) #11
• fixed the "warping" (credits to @mabe-at) #10
• added a link to this GH repo in the impressum because it's OSS ;) #8

Please consider merging so that these issues and PRs can be closed after 1 month.

[0x5ECF4ULT]

Small sidenote: something got messed up after I tried to merge your recent changes (see df5f711).