Use 80 chars, not 100

The lines in the files of this project are most often 80 chars or less,
so let's use that as the convention for this project.

Author: mhucka

.yamllint.yaml

@@ -19,7 +19,7 @@
 
 rules:
   line-length:
-    max: 100
+    max: 80
     # When the last item on a line can't be broken (e.g., a URL as a value),
     # it's rarely useful to flag it. The next 2 settings save developer time by
     # not requiring comment directives to disable warnings at every occurrence.