Allow relative path in virtualenv context manager
Also set env.user and env.hosts in vagrant context manager
Add task to require git command line tool
Fix Python 2.5 compatibility
Clear shell environment variables before sed/append

Functional tests would break at this point when using an HTTP proxy,
which injects a http_proxy environment variable.
Abort on nginx configuration errors
Upgrade default Node.js version to 0.10.7
Prepare 0.14.0 release