Fix hard-coded new line separator

setup.cfg

@@ -1,6 +1,6 @@
 [metadata]
 name = fsub
-version = 0.0.3
+version = 0.0.4
 author = Augusto Lenz Gunsch
 author_email = augustogunsch@tutanota.com
 description = CLI SubRip editor

src/fsub/fsub.py

@@ -91,10 +91,10 @@ class Subtitle:
         return False
 
     def __repr__(self):
-        return '{}\n{} --> {}\n{}'.format(
-                self.number,
+        return '{}{}{} --> {}{}{}'.format(
+                self.number, os.linesep,
                 self.time_start, self.time_end,
-                os.linesep.join(self.content)
+                os.linesep, os.linesep.join(self.content)
         )