- Allow URLs for Go, Node, Java.
- Add 1mb and 100mb files.
- Add --port flag.
- Add README.md.

Change-Id: If650bf88e705de002cac31a82393c7da104b355e
Reviewed-on: https://code-review.googlesource.com/c/gocloud/+/44013


Reviewed-by: Emmanuel Odeke <[email protected]>
Reviewed-by: kokoro <[email protected]>