Pick up vendored dep versions if possible

[freeformz]

Reported here: kubernetes/node-problem-detector#7

[freeformz]

This is because github.com/hpcloud/tail vendors a a version of gopkg.in/fsnotify.v1 that doesn't import golang.org/x/sys/unix. But godep flattens vendor folders and pulls up the dependency, so that there is only a single top level vendor directory. This required a version of gopkg.in/fsnotify.v1 be installed in the $GOPATH. The version vendored in hpcloud/tail is "7be54206639f256967dd82fa767397ba5f8f48f5" (1.2.1), while the version vendored in node-problem-detector is "30411dbcefb7a1da7e84f75530ad3abe4011b4f8".

[freeformz]

At some point godep should start taking a look at the versions of vendored deps and throwing an error if they (a) conflict or (b) what it would copy would be different.