Custom slider sizing available

This commit will make available to size sliders like this:
sliders: {
            saturation: {
              maxLeft: 307,
              maxTop: 307,
              callLeft: 'setSaturation',
              callTop: 'setBrightness'
            },
            hue: {
              maxLeft: 0,
              maxTop: 307,
              callLeft: false,
              callTop: 'setHue'
            },
            alpha: {
              maxLeft: 0,
              maxTop: 100,
              callLeft: false,
              callTop: 'setAlpha'
            }
          },