New grid function examples and documentation

-Added some tests to try and create abstractions away from typeset (for
easier updating).

-Added more documentation to typography.

-Added documentation to functions.scss

-Added documentation to variables.scss

-Cleaned up comments.

-Added a new breakpoint to main.scss to test grid functionality.

-Changed typography functions to allow for variable modular type at
different breakpoints.

-Added test for more responsive type to app.scss