fix building ruby package

Update version to 0.15.0

Allow Node users to set a custom logger and log verbosity.

Doc Fixit: Ordering and thread-safety for C++ streaming (sync/async) APIs

Fix C# nuget build (and all distribtests)

Fix build node package

Prevent race with grpc_completion_queue_shutdown.

Use GRPC_PYTHON_CFLAGS/GRPC_PYTHON_LDFLAGS in setup.py.

Changed %lld to use mingw supported PRId64

Brought compression spec up to date wrt error statuses

This is needed for building grpcio with mingw, see
https://github.com/grpc/grpc/pull/7012.

Remove generated NewClient factory method for C#.

Enable treating warnings as errors in objc tests

Update examples with Cocoapods 1.0.0

Const correctness for ClientContext and ServerContext getters

Updated grpcio c extension build for windows to use mingw.

The default compiler for Python c extensions is VS2008
or VS2010 depending on the Python version.  Since c-core
moved onto the c99 standard, these compilers are not
compatible.

Update podfiles with cocoapod 1.0 required fields

Add a test of metadata, status code, and details

Ignore unused variables in ruby compilation

Initialize port to -1

Added compression spec