[RTM] Install/Update Vendors via Copy

Description: Override copy strategy to allow vendors to be installed locally before the code is zipped and pushed to remote server. This reduces the dependencies required on the remote server and solves the issue with private [repository access] (https://github.com/everzet/capifony/pull/340/commits).

Symfony2 and composer only.

Bug fix: no
Feature addition: yes
Fixture addition: no
Backwards compatibility break: no
Tests: pass
Fixes the following tickets: #241

Todo:

- [x] Ideally I would like to extend the capistrano copy strategy with a capifony copy strategy. I couldn't figure out how to do this nicely so I have overloaded the copy strategy deploy method for now.
- [x] Not entirely sure where this should belong in terms of folder structure, should I mirror the capistrano directory structure for strategies?
- [x] Need to avoid new implementation of composer methods.

```ruby
set :deploy_via,  :capifony_copy_local
set :use_composer, true
set :use_composer_tmp, true
```