Please package testsuite to the distribution tarball

[mcepl]

I would like to fix packaging for OpenSUSE, but your release tarball does not contain the tests directory. Could you please distribute them as well?

Also, as it stands, your tests require standalone mock package, which is unnecessary and this patch makes it work with any recent (>= 3.3) Python:

---
 tests/__init__.py       |    1 +
 tests/test_arxiv2bib.py |    2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

--- /dev/null
+++ b/tests/__init__.py
@@ -0,0 +1 @@
+# This file intentionally left blank.
--- a/tests/test_arxiv2bib.py
+++ b/tests/test_arxiv2bib.py
@@ -2,7 +2,7 @@
 
 import arxiv2bib as a2b
 import unittest
-from mock import patch, Mock
+from unittest.mock import patch, Mock
 from xml.etree import ElementTree
 try:
     from StringIO import StringIO