Fix spec/cli issue on install

Fix for this error on install for 1.0.0.pre2 version :

-> % bundle install                                                                                                                
Using unindent (1.0) 
Using ghost (1.0.0.pre.2) from git://github.com/bjeanes/ghost (at master) 
ghost at /home/vnorguet/.rvm/gems/ruby-1.9.3-p484/bundler/gems/ghost-5b2d23e2fb49 did not have a valid gemspec.
This prevents bundler from installing bins or native extensions, but that may not affect its functionality.
The validation message from Rubygems was:
  ["spec/cli"] are not files

Using bundler (1.3.5) 
Your bundle is complete!
Use `bundle show [gemname]` to see where a bundled gem is installed.