Refactor LocalRepoApi

- Refactor LocalRepoApi module into a LocalRepository class for cleaner
  front-end usage, and removal of repetitive passing of function
  arguments for repository path and commits encountered. Convert all
  functions into class methods.
- Rename model package to git.
- Remove localrepoapi package and move LocalRepository into git package.
- Clean up documentation to meet spec.
- Edit main to test LocalRepository object