missing function BuildResources

``` bash
$ go build ./...
# github.com/jimenez/mesoscon-demo/client
client/main.go:55: undefined: lib.BuildResources
$ grep -e Build client/main.go 
                if err := demoLib.LaunchTask(offer, lib.BuildResources(0.1, 0, 0), &task); err != nil {
```
