Release Denominator 4.1

It's time to release Denominator v4.1

This updates to Feign 5

Current Progress:

[x] update README.md and denominator-cli/README.md
[x] bump 4.x branch to 4.1.0-SNAPSHOT
[x] release 4.1.0 from 4.x branch, publishing to maven central
[x] add denominator-cli version 4.1.0 to bintray, uploading the fat jar as denominator-cli/release/4.1.0/denominator
[x] Update the homebrew formula with the latest bintray content
[x] verify that 4.1.0 is in maven central
[x] communicate via irc, google groups, twitter etc.

Netflix / denominator