Make an ipynb about adding a feature

[emgrasmeder]

I think we need an example of how to do feature engineering --- probably as a file called Feature_Engineering.ipynb in the root folder.

• We could use cpi as an example, taking a table from the Ecuadorian census bureau and showing how to make it the right shape for our bigTable
• We could explain how to add oil prices to the bigTable

Data to be permanently used for bigTable should be submitted to us as a public dropbox link, and then we can add it to the s3 bucket on approval.