part 3 pandas issue

[paulbsalamanca]

Finished up pt 3 with Farnam:

1. some issues with "Applying a Function" in Step 3. certain Pandas versions seem to have issues with making a new column in this way:
   df['above_poverty_line'] = df['poverty_level'].apply(assign_level). need to use .loc

2. might be useful to add more reinforcement about the difference between attributes and methods, e.g., why df.shape vs. df.info()