In tox, write output to subdir

Write the index and ical files to a subdir with their 'correct'
names so that it is easier for the publish job to work.  It will
also be easier for developers to examine the output locally.

Change-Id: I810438e95791e1614f7ad10bb0419dea89f3893e
Depends-On: Ic188c1849559a9c8f282845940f56cf533b9bfd6

.gitignore

@@ -2,5 +2,5 @@
 doc/build
 *.egg-info
 pbr*.egg
-output.ical
 .*sw?
+output

tox.ini

@@ -12,4 +12,7 @@ deps = -r{toxinidir}/test-requirements.txt
 commands = {posargs}
 
 [testenv:ical]
-commands = yaml2ical -y meetings -o output.ical -t meetingindex.jinja -w output.html -f
+commands =
+    mkdir -p output
+    yaml2ical -y meetings -o output/irc-meetings.ical \
+        -t meetingindex.jinja -w output/index.html -f