Install pytest-bdd (which will eventually replace behave)

- Copy over the current tests from behave into the new directory that
  pytest-bdd will use them in

Co-authored-by: Micah Jerome Ellison <micah.jerome.ellison@gmail.com>

tests/features/journals/markdown-headings-335.journal

@@ -0,0 +1,42 @@
+[2015-04-14 13:23] Heading Test
+
+H1-1
+=
+
+H1-2
+===
+
+H1-3
+============================
+
+H2-1
+-
+
+H2-2
+---
+
+H2-3
+----------------------------------
+
+Horizontal Rules (ignore)
+
+---
+
+===
+
+# ATX H1
+
+## ATX H2
+
+### ATX H3
+
+#### ATX H4
+
+##### ATX H5
+
+###### ATX H6
+
+Stuff
+
+More stuff
+more stuff again