Adds landscape.io badge to README

[skip ci]
Turns 'info' and 'showfiles' into unpackers
Factors get_plugins()
Makes unpacker setup functions accept kwargs
Adds generic plugins
Adds parse signals
WIP
Only sets selected_unpacker to an unpacker
Adds 'subparsers' argument to pre_parse_args
Print traceback before calling warn()

Depending on warnings setup, warnings.warn() might raise, so the next
line might not be reached.
Merge branch 'plugins' into 'vistrails-integration'
Generates CLTools module
Adds missing packages to reprounzip/setup.py
Makes .vistrails/CLTools directories if absent
Works around VisTrails <=2.1.4 stdout bug
Makes vistrails plugin actually call reprounzip
Adds REPROUNZIP_NON_INTERACTIVE env variable
Merge branch 'plugins' into 'vistrails-integration'
Sets REPROUNZIP_NON_INTERACTIVE
Turns __main__ code into run_from_vistrails()