Enable testing with pypytox_add_pypy

This involved:

- Adding "pypy" to the `tox.ini` envlist.
- Adding `# doctest: +IGNORE_EXCEPTION_DETAIL` to 2 doctests, because the
  traceback message text is slightly different on PyPy.

1 files changed, 1 insertions, 1 deletions

diff --git a/tox.ini b/tox.ini
index d50d433..b54d5ec 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = py26, py27, py34, py35
+envlist = py26, py27, py34, py35, pypy
 
 [testenv]
 deps=