ENH: Smaller test dataset (320MB)

We'll see if Travis can actually run this. I have a bad feeling that, with all the additional tests that will be run, we will exceed the ~50-minute limit.
It's really a stylistic preference, since they're functionally equivalent. 

I find this syntax more explicit. When I read these types of lines, the paretheses tell me:

"I'm assigning a value to the left variable", and then I can see "its value is the result of a boolean comparison"

When I see the (functionally) equivalent `is_main = __name__ == '__main__'` in code, I inevitably read it as:

"I might be assigning the left and the middle variable to the right variable, or I might be assigning the left variable to a boolean, and I need to correctly count the number of equals signs in the second operand to figure it out"

This requires more effort for me. It also helps prevent bugs / typos where one could mean to type `is_main = __name__ == '__main__'` but forgets, and instead puts `is_main = __name__ = '__main__'`. This results in the sort of bug that is very difficult to catch and can even lead to security problems in some languages.