add support for virtual hosts

examples/vhosts.py

@@ -0,0 +1,18 @@
+from sanic.response import text
+from sanic import Sanic
+
+# Usage
+# curl -H "Host: example.com" localhost:8000
+# curl -H "Host: sub.example.com" localhost:8000
+
+app = Sanic()
+
+@app.route('/', host="example.com")
+async def hello(request):
+    return text("Answer")
+@app.route('/', host="sub.example.com")
+async def hello(request):
+    return text("42")
+
+if __name__ == '__main__':
+    app.run(host="0.0.0.0", port=8000)