0.34 rc

Supersedes https://github.com/CocoaPods/CocoaPods/pull/1143 

Sister: https://github.com/CocoaPods/Core/pull/160
```
~/Documents/Projects/irrationalfab/Rainforest/CocoaPods
⊙  rbenv shell 1.8.7-p374

~/Documents/Projects/irrationalfab/Rainforest/CocoaPods
⊙  bacon  spec/unit/external_sources/downloader_source_spec.rb

Pod::ExternalSources::DownloaderSource
  ✓ creates a copy of the podspec (65 ms)
  ✓ marks the Pod as pre-downloaded (44 ms)
  ✓ returns the description



3 specifications (3 requirements), 0 failures, 0 errors
```