Second version of the automated builds.
  - Define REQUEST_BUILD_RELEASE, the group of people that can
    create an issue reuqesting the release.
  - Define APPROVE_BUILD_RELEASE, the group of people that can
    approve the build of a release, and upload it.
  - The build doesn't start until it is signed.
  - Use labels to mark the status of the build.
  - Fail gracefully when not able to create the release, or the
    release name does not match the regular expression
Merge pull request #202 from nclopezo/auto-build-fixes

Second version of the automated builds.