Wily

* Support multiple metrics in graph command
* Git archiver will now check for existence of '.wily/', '.wily/**/*', '.wily', and others in .gitignore
* Introduce a new `--output` flag to the graph command to specify output HTML file instead of opening file in browser.
* Added toggle for disabling the .gitignore check in git archiver
* Add an --skip-ignore-check option to `wily build` to skip the checking of .gitignore
* Remove references to the mccabe algorithm as it's not implemented

* Complete support for pre-commit

* Fix a bug where .gitignore was not being passed correctly

* Add a 'diff' command to show the metrics changed values between the last index and the current data.

* Build now compares existing git history with the cached history and only builds the missing revisions instead of building the entire index
* Will check if .wily/ is not in .gitignore before running build
* Improved documentation..

* The build command now requires the target path, and supports multiple paths. Is no longer -t option, but an argument. This is to prevent the user from accidentally trying to scan venv's
* Operators all have a default metric (lines-of-code, maintainability-index)
* Report command by default will now display the default metrics in an index
* Report command now accepts multiple metrics and adds them to the table