Bump godeps

- DestroyError is now set in a thread-safe manner in main_test

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>
Open downloadedFile in goroutine to avoid race

- writeTarTo goroutine was the only thing using downloadedFile
- there is now a small risk the goroutine might hang and the downloadedFile will never get closed

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>