Make sure that relativize supports :path that is CWD (".")

[sikachu]

See #76. Basically:

The vagrant plugin development guide uses gem "my-plugin", path: "." instead of gemspec.

source 'https://rubygems.org'

group :development do
  gem "vagrant", git: "https://github.com/mitchellh/vagrant.git"
  gem 'appraisal', '~> 1.0'
end

group :plugins do
  gem "vagrant-rackspace", path: "."
end

This doesn't work either, probably because support for rewriting path wasn't completed/merged (#19). The result:

$ bundle exec appraisal install
bundle check --gemfile='/Users/Thoughtworker/repos/rackspace/vagrant-rackspace/gemfiles/latest_stable.gemfile' || bundle install --gemfile='/Users/Thoughtworker/repos/rackspace/vagrant-rackspace/gemfiles/latest_stable.gemfile'
Resolving dependencies...
Bundler can't satisfy your Gemfile's dependencies.
Install missing gems with `bundle install`.
Fetching gem metadata from https://rubygems.org/..........
Resolving dependencies...
Could not find gem 'vagrant-rackspace (>= 0) ruby' in source at ..
Source does not contain any versions of 'vagrant-rackspace (>= 0) ruby'

[sikachu]

I've confirm the bug — this is because we don't do path rewrite on the generated gemfile. So, for example, I have this Gemfile:

source "https://rubygems.org"

gem "appraisal"

group :plugin do
  gem "test", path: "."
end

And this is what's in the generated gemfile:

# This file was generated by Appraisal

source "https://rubygems.org"

gem "appraisal"

group :plugin do
  gem "test", :path => "."
end

We should actually lookout for path key on the DSL method that supports it.