behavior change to utils.get_command_output

Retuns a dictionary of ret, stdout, stderr. This cleans up the code a bit
and makes all applicable information available in each invocation.

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>
Merge pull request #57 from battlemidget/patch-return-dict-for-command-output

behavior change to utils.get_command_output
Pulling latest command output changes into this feature branch
Better error handling for charms not ready to relate

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>