v2.3.0

Changelog

d6bf51c Merge pull request #12 from grahamhayes/remove-conncurrency
8c76d95 Remove concurrency from "--all" operation
4c48aca add contribute button
13ed8a0 add contribute button
7466251 add docker pulls to readme
4f4ff2d cloudflare: add concurrency w/o closing on domain
8e13af8 fix merge conflict