use tailhead instead of tailer so as to handle rotating logs

requirements.txt

@@ -1,2 +1,2 @@
 raven>=3.3.2
-tailer>=0.3
+tailhead

sentrylogs/parsers/__init__.py

@@ -1,7 +1,7 @@
 """
 Log file parsers provided by Sentry Logs
 """
-import tailer  # same functionality as UNIX tail in python
+import tailhead  # same functionality as UNIX tail in python
 
 from ..helpers import send_message
 
@@ -27,22 +27,24 @@ def follow_tail(self):
         Read (tail and follow) the log file, parse entries and send messages
         to Sentry using Raven.
         """
+
         try:
-            logfile = open(self.filepath)
+            follower = tailhead.follow_path(self.filepath)
         except (FileNotFoundError, PermissionError) as err:
             raise SystemExit("Error: Can't read logfile %s (%s)" %
                              (self.filepath, err))
 
-        for line in tailer.follow(logfile):
+        for line in follower:
             self.message = None
             self.params = None
             self.site = None
 
-            self.parse(line)
-            send_message(self.message,
-                         self.params,
-                         self.site,
-                         self.logger)
+            if line is not None:
+                self.parse(line)
+                send_message(self.message,
+                             self.params,
+                             self.site,
+                             self.logger)
 
     def parse(self, line):
         """