python-cryptography: Extend recipe to support Python 3

- Add Python 3 recipe
  - Change DEPENDS and RDEPENDS code style
  - Add native and nativesdk to BBCLASSEXTEND

Signed-off-by: Fabio Berton <fabio.berton@ossystems.com.br>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>

meta-python/recipes-devtools/python/python3-cryptography_1.4.bb

@@ -0,0 +1,10 @@
+inherit pypi setuptools3
+require python-cryptography.inc
+
+SRC_URI += " \
+    file://run-ptest \
+"
+
+RDEPENDS_${PN} += " \
+    ${PYTHON_PN}-lang \
+"