Reconsitute options as strings

The argument to the --limit option is specified to be of type int.
When reconsituting the command line options, the attempt to 'join'
this to a string fails under some Python variants.

Ensure the str() representation of all option values is used in
the reconstitution.

Fixes #2
Handle unicode responses from paramiko in Python 2

Paramiko returns unicode strings, even in Python 2. Deal with this
by decoding all responses and converting them to strings.

Fixes #3