Use trim to handle VIRTUAL_HOST values with spaces

[mariusGundersen]

based on latest docker-gen

[jwilder]

Thanks @mariusGundersen!

[md5]

Even with this change, there will still be problems with spaces if any custom config files are used since the $host variable will still have extraneous space in those exists checks. I think it would be best to do something like {{ $host := trim $host }} (and the same for $proto).

[jwilder]

Good point @md5