Add branch coverage and decrease coverage minimum to 96

Author: grantjenks

tox.ini

@@ -79,7 +79,7 @@ line_length = 79
 addopts=
     -n auto
     --cov-branch
-    --cov-fail-under=100
+    --cov-fail-under=96
     --cov-report=term-missing
     --cov=diskcache
     --doctest-glob="*.rst"