Add a TOC and vim instructions

[llimllib]

• I wanted to test out the vim syntax, and documented how I installed it
• I used this program to generate the TOC.

[paulsmith]

@llimllib the indenting/level nesting on the TOC looks a little off from what I would expect. For example, "Installing Pushup" and "Creating a new Pushup project" are <h3>s, so I would expect then to be children of the "Getting Started" <h2>.