Add MLB scoring summary to Boxscores

[roclark]

Is your feature request related to a problem? Please describe.
The MLB Boxscores class should include a property which exposes the games final scoring summary. This will give end-users the ability to see how many points each team scored in every inning.

Describe the solution you'd like
One possible solution would be to create a dictionary with the scoring summary and differentiate between both teams, similar to the following:

scoring_summary = {
    'away': [5, 0, 1, 0, 0, 0, 0, 1, 0],
    'home': [1, 0, 0, 0, 1, 0, 0, 0, 0]
}

In the case of extra innings, additional elements can be added as necessary to the scoring summary.

Describe alternatives you've considered
A couple other options would be to create separate properties for the home and away teams, but the scoring summary is generally presented together and feels like a more logical coupling.

Another option is to extend the dictionary with further granularity similar to the following:

scoring_summary = {
    'away': {
        'first': 1,
        'second': 0,
        'third': 0,
        ...
    },
    'home': {
        'first': 5,
        'second': 0,
        'third': 0,
        ...
    }
}

This method doesn't feel elegant and the verbosity of the keys isn't entirely necessary. Plus, this becomes more difficult to utilize in scripts at the risk of clarity.