Adds missing unicode_literals from signals.py
Use ssh executable if available

This is for interactive sessions only; during tests or with --no-stdin,
paramiko will still be used.
Fixes escaping
Adds required SSH options
Merge branch 'use-ssh-exe' into 'master'
Adds --no-pty to 'vagrant run'
Adds missing explicit return statements
Fixes POSIX system detection

Not a problem now but be wary of future rpaths versions.
Merge branch 'master' into 'usage-stats'
Records run['argv'][0] for each run in pack
Adds REPROZIP_USAGE_URL env var
Records program name with version
Adds missing submit_...() call
Records pack details in load_config(file)
Don't submit report on UsageError
Adds 'usage_report' commands to enable/disable
Stores pre_setup and pre_run signals
Records more data