Fix linter warnings in examples/gps/main.py (#545)

Warnings:

* F401 kivy.clock.Clock imported but unused.
* E303 too many blank lines.

examples/gps/main.py

@@ -2,7 +2,7 @@
 from plyer import gps
 from kivy.app import App
 from kivy.properties import StringProperty
-from kivy.clock import Clock, mainthread
+from kivy.clock import mainthread
 from kivy.utils import platform
 
 kv = '''
@@ -33,7 +33,6 @@ class GpsTest(App):
  gps_location = StringProperty()
  gps_status = StringProperty('Click Start to get GPS location updates')
 
-
  def request_android_permissions(self):
  """
  Since API 23, Android requires permission to be requested at runtime.