Core transport & call cleanup

requiring tmpdir to resolve undefined method error

Core credentials API refactoring

Fixing NULL terminator for test cert.

Forgot to do that when I replaced the cert in #4096. Thanks asan for
catching that!

Updating the server1 cert so that it can be used with Go.

Merge release-0_11 into master

Handle Cancel before start.

Add missing grace value to server stop in Python example.

Update Python C wrapping layers to new credentials API

Fix dead link in doc

Generate all file lists and build target lists in binding.gyp from build.yaml

Fix naming issue in stress_test

(via ahh@google.com)
Under some configurations gRPC includes google3 base headers.  google3
has a namespace "thread" which mixes poorly with unqualified use of the
type std::thread; adding that namespace to various google3 headers
breaks this test.

Improve grammar/language for clarity

Fixes #4122

Add a useful __str__ method to face exceptions

Small typo of NodeJS version in README.md