Copy Swift's .mailmap to swiftclient repo

We had this before when swiftclient was in Swift's source tree, but it
didn't get copied over in the client extraction.

Change-Id: I218edcee265143164ea338e7ea95c19e72579925
Fix temporary pypy gate issue with setuptools

Adding a fix proposed in bug 1290562 to avoid continuous gate failures
because of setuptools issue reported in the bug linked above.

Temporary Fixes-bug: #1290562

Change-Id: Ia8616d1939e664fc82de030b6384acb235e5c101
Merge "Fix temporary pypy gate issue with setuptools"
Merge "Copy Swift's .mailmap to swiftclient repo"