use_version_file support; available_versions and _manifest
respecting use_version_file; calling available_version and _manifest
rake bump_build to 1.0.1.2
added Buildar#gemfile

this helps support the :install task and cleans up :publish
includes a provisional fix for #available_version
rake bump_build to 1.0.1.3
rake bump_build to 1.0.1.4
added :install, simplified :publish
use_version_file and _manifest_ default to false