feat: add ff-tool --version flag (#89)

* feat: add --version flag
Closes #61

* style: flake8 fix

fftool/arg_parser.py

@@ -74,4 +74,11 @@ def arg_parser():
               directory"
     )
 
+    parser.add_argument(
+        '-v',
+        '--version',
+        action='store_true',
+        help="Print ff-tool version, then quit."
+    )
+
     return parser.parse_args()

fftool/main.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python
 
 from outlawg import Outlawg
-from fftool import PATH_PREFS_ROOT
+from fftool import PATH_PREFS_ROOT, __version__
 from arg_parser import arg_parser
 from firefox_download import download
 from firefox_profile import create_mozprofile, clean_profiles
@@ -14,6 +14,10 @@ def main():
     Log.header('FF-TOOL: download, install & launch Firefox!', 'XL', '=')
     options = arg_parser()
 
+    if options.version:
+        print('FF-TOOL VERSION: {0}'.format(__version__))
+        return
+
     if options.app and not PATH_PREFS_ROOT:
         Log.header("ERROR")
         print("Missing path to $PATH_PREFS_ROOT directory.")