Github quarterly contributions

Adds a quarterly stats button on a user's landing page

Adds a "Add previous quarter" button to a user's Github landing page (see screenshot). Pressing this button fetches the last quarter worth of commits, prs, and issues for the user. Subsequent presses goes back additional quarters. Note: this will include private commits/prs/issues if you are the current logged in user. Viewing someone else's page will only return their public activity. Source: https://github.com/ebidel/github-quarterly-stats