Flagging the release.

Fix Python unit tests

Fixing the absence of 'tag' in the version.

Node Mac artifact build fix

Use precompiled extensions only

Truncate Python target triple for custom bdists

Make a couple of fixes to distribution build and tests

Fix fedora21 distribtests for python and ruby

Fix node distrib test on Debian Jessie x86

Backport: Fix python centos6 distribtest in release-0_13

Reorder Python artifact commands.

Paper over custom command limitations

The custom gRPC bdist command depends on numerous undocumented and
private behaviors of setuptools, wheel, distutils, etc. One such is the
ordering of generated distribution targets. We paper over this under the
assumption that the command will only be useful for gRPC devs, and
document with a command description a contractual obligation of users of
the command.

Bundle node-pre-gyp with the node package

Use wheels instead of eggs for custom bdists.

Ruby distribtests on Linux

Fixing Ruby examples.