Run setup.py gen_tl when installing (may fix #271)

setup.py

@@ -42,8 +42,7 @@ class TempWorkDir:
         os.chdir(self.original)
 
 
-def main():
-    if len(argv) >= 2 and argv[1] == 'gen_tl':
+def gen_tl():
     from telethon_generator.tl_generator import TLGenerator
     generator = TLGenerator('telethon/tl')
     if generator.tlobjects_exist():
@@ -56,6 +55,11 @@ def main():
     )
     print('Done.')
 
+
+def main():
+    if len(argv) >= 2 and argv[1] == 'gen_tl':
+        gen_tl()
+
     elif len(argv) >= 2 and argv[1] == 'clean_tl':
         from telethon_generator.tl_generator import TLGenerator
         print('Cleaning...')
@@ -78,8 +82,11 @@ def main():
 
     else:
         if not TelegramClient:
-            print('Run `python3', argv[0], 'gen_tl` first.')
-            quit()
+            gen_tl()
+            from telethon import TelegramClient as TgClient
+            version = TgClient.__version__
+        else:
+            version = TelegramClient.__version__
 
         # Get the long description from the README file
         with open('README.rst', encoding='utf-8') as f:
@@ -89,7 +96,7 @@ def main():
             name='Telethon',
 
             # Versions should comply with PEP440.
-            version=TelegramClient.__version__,
+            version=version,
             description="Full-featured Telegram client library for Python 3",
             long_description=long_description,