Do not fail if git is not installed.
Remove :preserve flag from cp_r.

This can fail with symlinks that point to nothing.
Add changelog for 0.16.1.
Bump version to 0.16.1.

Changes:

* Unbreak package building with broken symlinks.
* Do not fail if git is not installed.
Add comment why :preserve got removed.
build omnibus packages in tmp-dest

This is a breaking change! However, it improves consistency between
omnibus and regualar recipes. Regular recipes usually contain the
following:

    def build
      configure :prefix => prefix
      make
    end
    def install
      make 'DESTDIR' => destdir
    end

Omnibus recipes on the other hand looks like this:

    def build
      configure :prefix => destdir
      make
    end
    def install
      make
    end

With this patch, both can use the first form. Moreover building omnibus
packages without write privileges in /opt is now possible.

fixed the previous commit

added documentation