Support colors in individual cells of the table.

There is often need to highlight particular cells in a table. To achieve that there needs to be a way to specify a style for each cell and corresponding logic for it.
To support this, if a cell needs particular style, an object with msg and style properties need to be passed.

Sample:
var Table = require('cli-table');

var table = new Table({
        head: ['Rel', 'Change', 'By', 'When']
      , style: {
            'padding-left': 1
          , 'padding-right': 1
          , head: []
          , border: []
        }
      , colWidths: [6, 21, 25, 17]
    });


table.push([{msg: 'Hi'}, {msg: 'Hello',style: ['blue']}, 'Hi', 'Hi']);

ran npm test to ensure sanity of the build