Migrate library to kotlin, Update Libraries and Small Improvements

[BharathKSunil]

Changes:

• Incremented gradle version.
• Moving core library to kotlin
• Replaced calling invalidate immediately. Why?

  protected void dispatchDraw(Canvas canvas) {
  ...
  if (mIsRunning) {
              invalidate();
          }
  }

  with

  override fun dispatchDraw(canvas: Canvas) {
  ...
  if (isRunning) {
              ViewCompat.postInvalidateOnAnimation(this)
          }
  }