remove TrimLeft as it's go1.1
Merge pull request #794 from dotcloud/780-diff-fix2

- Runtime: remove TrimLeft as it's go1.1
Bumped version to 0.4.0
Fixed missing Body.Close when doing some HTTP requests. It should improve some request issues.
Minor changes in registry.go
Disabled HTTP keep-alive in the default HTTP client for Registry calls
Merge pull request #797 from dotcloud/registry-fix-missing-body-close

registry.go: Fixed missing Body.Close()