Update Puppetfile
Don't die if HEAD ref is not symbolic.

Examples of situations when HEAD is not symbolic:

 * You're doing interactive rebase
 * You're using git bisect
 * ... and so on.
allow bundler 1.x releases
Merge pull request #126 from indirect/bundler_update

Allow Bundler 1.x releases
It's cleaner to have another case: "not on any branch".
Merge pull request #123 from paxan/dont-die-when-head-is-detached

Don't panic if your HEAD is detached
Merge pull request #116 from pedrogimenez/patch-1

Update Puppetfile