+ find the golang download url generically

  - try to check the following download locations in order

      1. http://golang.org/dl
      2. http://go.googlecode.com/files

    Otherwise, bail out with an error message.
+ alternative way to get golang download url generically

  - looks like the http://go.googlecode.com/ doesn't respect
    HEAD requests.  This alternative approach is less rigorous
    than the prior approach, but it seems to work.

  - removed the 'warn' and 'die' helper functions because they weren't
    used in this 2nd pass approach.