tutorials fail doctests

[mpenkov]

If you run "python -m doctest docs/src/tut1.rst" you get a ton of output. Most of the problems are because of incorrect formatting, e.g.

>>> x = [1,
>>>      2]

should really be:

>>> x = [1,
...      2]

For whatever reason, it doesn't look like the tutorials were ever tested with doctest. There's no reason for it to be this way, so we should make them doctest-compatible in the future.