interactive: list_spi: Accept and split string as first argument

Use case: to show info on all packages in your clipboard, do:

>>> list_spi('''
... <paste>
... ''')

port_stats/interactive.py

@@ -170,6 +170,8 @@ g = gspi  # noqa
 
 
 def list_spi(pkgs, colors=None, to=print):
+    if isinstance(pkgs, basestring):
+        pkgs = pkgs.split()
     pset = frozenset(pkgs)
     lines = _spi_by_predicate(pset.__contains__, colors)
     unknown = pset - frozenset(BY_NAME)