Add draft support

[amarvin]

No description provided.

[amarvin]

Note that VOR calculation isn't accurate pre-draft (#48).

[amarvin]

To get rough VOR before a draft, can edit scraper.py to be like:

    # Calculate VOR
    columns = ["Week {}".format(i) for i in range(current_week(), 18)]
    df["Remaining"] = df[columns].sum(axis=1)
    df.sort_values(by="Remaining", ascending=False, inplace=True)
    available = df.loc[df["Owner ID"].isnull()]
    more_to_draft = {
        "QB": 20,
        "RB": 49,
        "WR": 57,
        "TE": 16,
        "K": 13,
        "DEF": 13,
    }
    drop_indexes = []
    for index, row in available.iterrows():
        positions = row["Position"].split(",")
        position = positions[0]  # TODO: pick their best position somehow
        if more_to_draft[position] > 0:
            drop_indexes.append(index)
            more_to_draft[position] -= 1
    available.drop(index=drop_indexes, inplace=True)
    means = (
        available.groupby(["Position"])["Remaining"].nlargest(3).groupby(level=0).mean()
    )