make some spacing changes to the main page

there are other things that i want to do, but not being a designer/in charge of this project, i'll list some of my ideas here:

- there's too much info (IMO) on the main page. i think it should be a pithier elevator pitch. if it could be boiled down to "data model", "operation", and "visualization" i think that would go further in making the initial "sale" ("what is it? how does it work? how can I use the data?")
- needs color. i'm terrible at this. but it's a lot of black.
- a lower section with some more detail, about the main 3 points. couple pictures per section adding visual info, e.g. picture of an example data set to show the dimensionality, a gif of a terminal running a compile and scp'ing the final single binary, and a graph showing what visualization can look like
Fallback to Open Sans only works if you do `font-family: Avenir, "Open Sans"`