Always use the current_path when working with unicorn, and make sure unicorn uses the correct BUNDLE_GEMFILE when reloading
updates to address issue #10 and #11

- Changed default location of `:unicorn_pid`
- Depend on capistrano => 3.1.0
- Added `:unicorn_bundle_gemfile` to override `:bundle_gemfile`
- Bugfix; use current_path vs release_path
move context
Merge pull request #12 from tablexi/issue-10

address issue #10