[WIP] Add functions for working with interleaved experiments
- Functions for working with interleaved search results experiments; see ?interleaved for details
- interleaved_preference() calculates the preference statistic from click data according to Eq. 4 from Chapelle et al. (2012) paper on interleaved search evaluation
- interleaved_bootstraps() resamples sessions with replacement to generate a sample of preferences
- interleaved_confint() computes a confidence interval from a bootstrapped sample of preferences
- These require a C++11-compatible compiler
- C++-based exact_binomial() to estimate sample size for exact binomial tests
- Misc. things changed with this patch:
- ggplot themes theme_min() and theme_facet()
- Documentation updates (including a vignette on interleaved experiments)
- Syntax-checking unit test
- MIT licensing