TaskHero Release v2

In our second release of TaskHero, we have implemented a few key features.

1. We have separated our code into two main mods: app.rs and gamification.rs. These are the two files that will be in accordance with one another. App.rs will be the main function for rendering the gui and its components, especially tasks, achievements, challenges, etc. For gamification.rs, this is going to be used for the gamified pieces of our application. We will update these as we go, as some of the features that are currently in app.rs and gamification.rs could switch around or move to other functions/ methods accordingly.
2. We have further implementation for the challenges, where users can complete daily challenges and weekly challenges for "reward points." This can change, but it is based on the number of tasks completed per day and once a day for a week.
3. We have further implemented statistics on the tasks completed- meaning a report on the completed tasks, what priority level these tasks are, how many are low, medium, high, etc.
4. touched up some bugs (ex. we fixed the goal setting section to not allow for bronze number of tasks to be greater than silver, silver greater than gold, etc.)
5. Touched up the README.md to reflect this

Please do note, for this release, we were working with dockerfile, but it was not cooperating. This will take further discussion, but dockerfile will be implemented soon in the future.