Unified random number provider

- not used yet, just an inactive helper function
- I received feedback that OpenSSL.rand isn't more secure than
os.urandom. I read several debates/analyses about it and concur

src/helper_random.py

@@ -0,0 +1,9 @@
+import os
+
+from pyelliptic.openssl import OpenSSL
+
+def randomBytes(n):
+    try:
+        return os.urandom(n)
+    except NotImplementedError:
+        return OpenSSL.rand(n)