config.berkshelf.enabled should be explicitly set to true to make berkshelf take effect

[puncha]

As the README.md document says:

Enable Berkshelf. If a Berksfile exists or a berksfile_path is given, this

value is automatically set to true. If not, the value is false

config.berkshelf.enabled = true

But actually, it doesn't work even though I specify an existing berkshelf_path.