Summary:
* git mv
* codemod facebook::wangle folly::wangle
* Change 'runnable' to be a base class in wangle instead of thrift

Justification:
* std::future doesn't have then, whenall, etc.
* boost::future doesn't support executors

@override-unit-failures

Test Plan: contbuild and pray

Reviewed By: hans@fb.com

FB internal diff: D1185194