Use C extension in Python 3, and make Python version handle ``default`` the sameissue4

Fixes #4 and fixes #5.

Add a specific test case for both of these things.

Enabling the C extension on Python 3 revealed more places where
readonly attributes can raise different exceptions so fix those tests.

Also add Python 3.6 to the supported list, and use zope.testrunner to
workaround the namespace package issue.

1 files changed, 6 insertions, 0 deletions

diff --git a/.coveragerc b/.coveragerc
new file mode 100644
index 0000000..af40312
--- /dev/null
+++ b/.coveragerc
@@ -0,0 +1,6 @@
+[run]
+source = src
+
+[report]
+exclude_lines =
+    pragma: no cover