Merge pull request #252 from fedora-infra/feature/doc-split

Move topics doc out to another rtfd project
Remove this block now that doc_utilities is moved away.
Touching up/shuffling around docs.
Test the dict_query function in fedmsg.utils.
Merge pull request #253 from fedora-infra/feature/testing-utils

Test the dict_query function in fedmsg.utils.
Fix typo in head-consumer approach section
Adjust file header.
Add a new "replay" command.

This lays the foundation for fixing fedora-infra/datanommer#18.
Add the actual code for the "replay" command.
Documentation for the replay command.
Fix bug identified in oddshocks/fedimg#1
Merge pull request #256 from fedora-infra/feature/replay

Add a new "replay" command.
Use more https links
systemd units: Shorten documentation URL