vector indexing

[delgadom]

it would be great if we could do something along the lines of:

>>> runs[[0, 1, 2]]
[{'rcp': 'historical',
  'model': 'obs',
  'year': 1950,
  'func': <function __main__.<lambda>(x, thresh)>,
  'thresholds': 32},
 {'rcp': 'historical',
  'model': 'obs',
  'year': 1950,
  'func': <function __main__.<lambda>(x, thresh)>,
  'thresholds': 90},
 {'rcp': 'historical',
  'model': 'obs',
  'year': 1950,
  'func': <function __main__.<lambda>(x, thresh)>,
  'thresholds': 95}]

it would be even cooler if we could use slices:

>>> runs[:3]
[{'rcp': 'historical',
  'model': 'obs',
  'year': 1950,
  'func': <function __main__.<lambda>(x, thresh)>,
  'thresholds': 32},
 {'rcp': 'historical',
  'model': 'obs',
  'year': 1950,
  'func': <function __main__.<lambda>(x, thresh)>,
  'thresholds': 90},
 {'rcp': 'historical',
  'model': 'obs',
  'year': 1950,
  'func': <function __main__.<lambda>(x, thresh)>,
  'thresholds': 95}]