This should make crane able to build images without any cache (if specified)

Hi, 

This is the pull request for #35

First time writing Go so I had a little problem with
```go
if nocache { 
something 
} else {
somethingelse
}
```

Thanks!

Signed-off-by: Scott M. Likens <scott@likens.us>
Much better; didn't know enough about go (and a quick glance confused me fast).