Updated the logo also in the README file.

Former-commit-id: 69c1a86d3bfca0ca9daa9bb59956a09d8887b294

README

  Welcome to the cosmological code
-    ______       __________________
-   / ___/ |     / /  _/ ____/_  __/
-   \__ \| | /| / // // /_    / /   
-  ___/ /| |/ |/ // // __/   / /    
- /____/ |__/|__/___/_/     /_/     
+    ______       _________________
+   / ___/ |     / /  _/ ___/_  __/
+   \__ \| | /| / // // /_   / /   
+  ___/ /| |/ |/ // // __/  / /    
+ /____/ |__/|__/___/_/    /_/     
  SPH With Inter-dependent Fine-grained Tasking
 
-www.swiftsim.com
+Website: www.swiftsim.com
+Twitter: @SwiftSimulation
 
 See INSTALL.swift for instructions.