change submodule reveal to reveal.js

* updated submodule to current version
* received error: submodule reference is not a tree
clarify ice breaker question
add git installation address to slide
remove redundant step from make a commit
add section with link to all Git GUIs

* gitk doesn't exist on my computer
removed strange command

* why is changing a file a command?
clarify git rm command
remove redundant section about reset
clarify header: committed not staged changes
whitespace: fix indentation
remove subsections (fix indentation)

* remembering to use the down arrow to navigate was too confusing
Merge pull request #1 from johnsons531/master

it's a start