Bug 1411683 - Add "requirements.txt" for pycert.py r=keeler

There are specific versions needed for security/manager/ssl/tests/unit/pycert.py,
so let's give PIP some installation help:

0.1.7 for pyasn1 and 0.0.5 for pyasn1_modules

(recent versions break pycert/pykey/pycms)

MozReview-Commit-ID: Fk98UPd8bJo

--HG--
extra : rebase_source : 79436d4e99cda1dca438015835fdfa83a78c4dc7

security/manager/ssl/tests/unit/requirements.txt

@@ -0,0 +1,6 @@
+lxml
+pyasn1 == 0.1.7
+pyasn1_modules == 0.0.5
+ecc
+mock
+rsa