Merge pull request #6 from embaldridge/master

Adds .gitignore file to exclude private data (NABA and CBC) from data repository, adds spab files for remaining data.
Merge pull request #7 from embaldridge/master

Updates to README, .gitignore file, and rough draft of analysis script.
Simplifies loop in model_comparisons function.
Adds log-likelihoods for geometric series, negative binomial.  Need to add code to calculate AICc weights.
Merge remote-tracking branch 'upstream/master'