tests: Big push to get the tests to pass again. - Lots of fixes everywhere in the code. - Try to handle debug logging in the multiprocessing worker pool when running in pytest. Not perfect, but usable for now. - Replace all `.md` test files with `.html` since now a auto-format extension always sets the format. - Replace `out` with `outfiles` in most places since now blog archives are added to the bake output and I don't want to add expected outputs for blog archives everywhere.

--- a/piecrust/plugins/base.py	Sun Oct 29 22:46:41 2017 -0700
+++ b/piecrust/plugins/base.py	Sun Oct 29 22:51:57 2017 -0700
@@ -171,6 +171,8 @@
         all_components = []
         for plugin in self.plugins:
             plugin_components = getattr(plugin, name)(*args)
+            # Make sure it's a list in case it was an iterator.
+            plugin_components = list(plugin_components)
             all_components += plugin_components
 
             if initialize: