CLA for PRs

[Antoine Toulme]

Hey folks,

I know this is a small contrib so it doesn’t require an explicit CLA:
https://github.com/apache/incubator-tuweni/pull/11 
<https://github.com/apache/incubator-tuweni/pull/11>

However, for larger PRs, how do we insist folks sign CLAs? Is there a process 
for this?

Cheers,

Antoine