1. Modernize the icons of buffer file state.
2. Beautify flycheck.
3. Fix #66: Add a segment for GitHub notifications.
4. Optimize: update persp name.
5. PR #65: Show Rust version in the modeline
6. Update screenshots (#64).
7. Make vcs more obvious.
8. Improve mouse-face for segments.
9. Make doom-modeline-column-zero-based and doom-modeline-percent-position global.
10. Fix #62: disregards value of column-number-indicator-zero-based.
11. Treat doom-modeline-def-modeline as a function.
12. Add unit test suite.
13. Other minor improvements.