Update for efficiencies

Code changes for efficiency:
-consolidated dealer_turn, find_winer, player_turn erbs to game erbs.
-added conditional buttons at different stages of the game
-added conditional html statements that appear when the dealer will hit.
-improved card_image helper method
-improved winner and end of game logic

Design improvements
-added welcome screen
-added logo to top of page
-added blackjack page to appear when blackjack is hit
-centered card images and put within colorful alert box
Improvements needed