add basic structure.

mathema/actor.py

@@ -0,0 +1,13 @@
+import asyncio
+
+
+class Actor:
+    def __init__(self, name: str):
+        self.name = name
+        self.inbox = asyncio.Queue()
+
+    async def send(self, msg):
+        await self.inbox.put(msg)
+
+    async def run(self):
+        raise NotImplementedError