simplify none commands to a list

simplify none commands to a list
remove none commands from help: FIX issue #33
FIX issue #36: last git has error

FIX issue #36: last git has error

https://github.com/timthelion/subuser/issues/36
add example for  --short

First it did not seem to work because I used: subuser list --short available

so adding an example would be good
replace system call 'ls' with pure python code

replace system call 'ls' with pure python code
Merge branch 'patch-3' of https://github.com/peter1000/subuser
Merge branch 'patch-2' of https://github.com/peter1000/subuser
Merge branch 'patch-4' of https://github.com/peter1000/subuser