Added ReadOnly segment

    + The segment displays a padlock (in patched mode), or 'RO'
      (in compatibility mode).

    ! Added a condition for showing / if that is the only path.
      The CWD segment earlier showed nothing, which I think is not
      very consistent.
Added error redirection to avoid stack traces.
Merge pull request #93 from SaswatPadhi/RO_Dirs

    Added ReadOnly segment
Merge pull request #94 from SaswatPadhi/CTRL-C

Added error redirection to avoid stack traces.