Re-add `Metadata.for_package` platform version truncation

This inadvertently got deleted in 0bfc7aa12.
Remove `homepage` from Artifact publisher path

Since any Artifactory repo used for storing Omnibus packages already
requires a custom layout we can safely remove any Maven-isms in the
path.
Merge pull request #265 from opscode/schisamo/artifactory-homepage-global-config

Remove `homepage` from Artifactory path
Add support for Windows 8.1 Update (6.3.9600)
Ensure parent directory exists in Builder#touch
Accept globbing patterns in Builder filesystem methods
Move windows_safe_path to Builder

This commit changes the way paths are represented in Omnibus. Prior to
this commit, paths would be operating-system-specific. However, with the
introduction of the new Builder DSL methods like +copy+ and +move+, Dir
globbing expects paths to be Rubyesque.

Now, all paths are represented using forward slashes (like the Unixes,
Darwins, and BSDs), and it is the responsibility of the software
writer to wrap command calls that shellout to the system in a call to
+windows_safe_path+.
Expand Project#install_dir relative to Config.project_root