Add prompt when there is no binary for node version greater than v1.0.0
Currently, on FreeBSD, if we try `nvm install 4.2`, we will only get:
> Installing node v1.0 and greater from source is not currently supported
In fact I had no idea what's wrong because I didn't use `-s` parameter for it,
and then I found that there are two reasons:
1. There was no pre-built nodejs binary from official for FreeBSD, which means we need to build from source.
2. nvm doesn't support build for v1.0 and greater version from source yet.
So I think there should be a prompt message to tell the user about the reason why nvm will go to build from source,
no matter it will succeed or fail.
Peter Dave HelloandPeter Dave Hello