Some decoration to the level 3 titles

[Issue #3]

These are section dividers in each slide. After some experiment, I think
some text underlines will do.
Use customize bullet for lists

[Issue #2]

Each list item now has a bright orange "#" in front as the bullet, this
is cooler than anything!
Rearrange list spacing

[Issue #2]

As level 3 headings are not shown now, I changed the top margin for
lists in these slides.
Use another color for the 2nd part of talk

[Issue #2]

The audience need to better know where I am in the talk. So I add a
little color coding to remind that I am talking about another project.