Governor Rick Perry made a stop this afternoon at a north Fort Worth Walmart store to kick off the tax-free weekend.   He says estimates are that shoppers will save nearly 60 million dollars.   He was joined by State Comptroller Susan Combs. She says Texas remains committed to helping families reap the benefits of a low-tax pro-business environment.    This is the 12th year the state has dropped the sales tax on a list of back-to-school items.