[fix] Mention requirement for gradle 4.10 in readme (#453)
[fix] Mention requirement for gradle 4.10 in readme (#453)

## Before this PR

We don't explicitly mention the version of gradle you need to use Baseline.

## After this PR

We mention this in the readme.

Fixes #367 

## TODO

- [ ] Run tests against gradle 4.10 to ensure compatibility (at least a basic application of `com.palantir.gradle-baseline`)
palantir/gradle-baseline,palantir/gradle-baseline