v1.1: Upgrade all dependencies (e.g., KaTeX 0.9)

Change log:

1. Upgrade package.json to use the latest dependencies;
2. Remove font files from the repository, use KaTeX's font files instead;
3. Test with the latest 0.8 version of KaTeX;
4. Fix a bug that makes all texts in math environment to lowercase.
5. Improve coding style of JS files;
6. Update README.md.