Support multiple documents per docker run

[dsperling]

It would be nice to support printing multiple pages of either Jira or Confluence in any order.
For example:

docker run --init -v $PWD:/output -e ATL_USERNAME=<user> -e ATL_PASSWORD=<pass> smithmicro/pdf \
  <jira-url1> <confluence-url1> <jira-url2> <confluence-url2>