Add timeout arg to discover()

diff --git a/discovery.py b/discovery.py
index 8f62f66..f411066 100644
--- a/discovery.py
+++ b/discovery.py
@@ -96,13 +96,13 @@ class ZeroconfListener(object):
         services[sname] = svc
 #         print "services[%s] = %s" % (sname, svc)

-def discover():
+def discover(timeout=3000):
     global browser
     lock = threading.Lock()
     lock.acquire()
     listener = ZeroconfListener()
     browser = Browser(args=('_ssh._tcp','_workstation._tcp','_nameserver._udp'))
-    browser.timeout = 3000
+    browser.timeout = timeout
     browser.lock = lock
     browser.set_listener(listener)
     browser.start()