function clean(str) {
  return str.replace(/[^A-Za-z\s]/g, ' ').replace(/[\s]+/g, ' ').trim().toLowerCase();
}
A representation of a cell within the table.
Implementations must have `init` and `draw` methods,
as well as `colSpan`, `rowSpan`, `desiredHeight` and `desiredWidth` properties.
@param options
@constructor