Parse git log data for repo statistics

This pull request introduces functionality that generates a git log from a repository, munges the log, and outputs a formatted CSV file for consumption by other programs.

## Major Changes

- Add a parser that calls, processes, and outputs formatted git log data
- Add a specifications.md file to detail the formats for input, output, and intermediate data processing
- Define the Loglet class: an intermediate data model (in Python) for holding the information about file changes in a given commit.