Merge pull request #1934 from reaperhulk/asn1string-to-utf8

refactor asn1string->utf8 conversion into a separate function
diff --git a/tox.ini b/tox.ini
index 759345f..77382eb 100644
--- a/tox.ini
+++ b/tox.ini
@@ -9,6 +9,7 @@
     pretend
     pytest
     ./vectors
+passenv = ARCHFLAGS LDFLAGS CFLAGS INCLUDE LIB LD_LIBRARY_PATH
 commands =
     # We use parallel mode and then combine here so that coverage.py will take
     # the paths like .tox/py34/lib/python3.4/site-packages/cryptography/__init__.py