Establish a release process and versioning strategy for nupic

[rhyolight]

NuPIC needs to start a release process, even if we begin with "alpha", "beta", etc. We need to get a process going to we can start to think about proper releasing. The first step is to prepare a release road map so everyone can see and discuss what issues should go in what release candidates.

First, we'll attempt to version the nupic repository, ignoring the details of nupic.core's separate versioning. The nupic.core version numbers will be independent of nupic, and will come later.

• Depends on nupic should build assuming nupic.core is a standard external library

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• Create release road map (@rhyolight)
• Introduce formal changelog file into codebase (@rhyolight)
• Document and enforce semantic versioning. (@rhyolight)
• NuPIC version number is defined in one place in the codebase (@rhyolight)
• Create a release tag trigger for release processing (@rhyolight)
• Configuration base class must use pkg_resources to find config file(s) (@rhyolight)
• Update setuptools setup to create proper sdists (@rhyolight)
• Upload complete nupic packages to pypi on every release (@rhyolight)
• Publish binaries build with GCC instead of clang (@rhyolight)
• Ensure platform-specific wheel files are produced during release (@rhyolight)
• Document release branch strategy https://github.com/numenta/nupic/wiki/Releases (@rhyolight)
• gcc error on pip source distribution install: OS X (@rhyolight)
• Linux pip installs from are downloading OS X binary package (@rhyolight)
• package_data is missing for linux wheels (@rhyolight)
• Linux wheels deploy to S3 on release (@rhyolight)
• Update README with new binary installation instructions (@rhyolight)