Update Traefik README.md

[cr0hn]

• Added an small FAQ
• Added usage examples
• Added new label 'traefik.frontend.rule', more useful to add your own domains

[rawmind0]

Hi @cr0hn , thanks for the PR and contribute. :)

Please, take a look at changes requested.

[rawmind0]

Thanks @cr0hn ...

LGTM