Removed redundant demo config code
Merge pull request #47 from Financial-Times/demos

Removed redundant demo config code
Overriding max widths now works. Fixes #43
Fixed readme and merged breakpoint and max width variables
Changed default max widths
Merge pull request #48 from Financial-Times/max-widths

Overriding max widths now works. Fixes #43
Fixed merge conflicts
Changes are now backwards compatible