SC + ITS: quantitative outputs

[drbenvincent]

Need to provide quantitative outputs/reports for synthetic control and interrupted time series.

The Causal Impact package provides these summary stats:

For the frequentist version: Add ability to test for presence/absence of causal impact. There is a traditional way of doing this, but we could also envisage bootstrap on the pre-intervention data.

TODO

• add summary stats for Bayesian ITS + SC (first pass)
• add relative impact as well as absolute
• Implement a better API
• add summary stats for Frequentist ITS + SC

[drbenvincent]

As of now, this is what we have for getting outputs /summary stats. It's a good start, but we need to make the API better :)