check if option in config exist

addressing:
Traceback (most recent call last):
  File "/usr/bin/tito", line 23, in <module>
    CLI().main(sys.argv[1:])
  File "/usr/lib/python2.7/site-packages/tito/cli.py", line 94, in main
    return module.main(argv)
  File "/usr/lib/python2.7/site-packages/tito/cli.py", line 635, in main
    auto_accept=self.options.auto_accept)
  File "/usr/lib/python2.7/site-packages/tito/release.py", line 473, in __init__
    overwrite_checkout = self.config.get(self.target, "remote_git_name")
  File "/usr/lib64/python2.7/ConfigParser.py", line 607, in get
    raise NoSectionError(section)
ConfigParser.NoSectionError: No section: 'git-sat'