Started work on a semantic demo
Adding more to the demo
Update README.md
Update README.md
Update README.md
Update README.md
created customisable grid, made breakpoints variables

Changed the variable setup and used Sass control directives to create a
grid that can be completely customised by editing two values in the
_gridvars file.

Breakpoints are now also variables and can be edited from the _gridvars
file.
made row widths variables, changed column width syntax

Row max-widths for different breakpoints are now editable variables
rather than fixed numbers.

The column width variable is now $column-unit instead of $grid-unit.
edited math.md to reflect new variables
housekeeping
housekeeping
edited breakpoint headers
Merge pull request #3 from rhysdoesdesign/dev

Added customisable grid support, fixes #2