Refractored css into js for flat-buttons

[mmrtnz]

• Created ColorManipulator utility file
  • Serves as the js equivalent to Less' color functions:
  • fade(color, amount)
  • lighten(color, amount)
  • darken(color, amount)
• Modified EnhancedButton, added a new prop
  • Given a onKeyboardFocus prop which notifies the parent button (e.g. FlatButton) to update its styling.
  • Will be utilized by future button refractoring: RaisedButton, FloatingActionButton
• Created Typography js file
  • Contains global styles from Typography.less
  • Other styles will be added as they are needed.