Unit4 Lesson2 Session1 - verify username before alter it to link
Unit4 Lession2 Session1-alter all usernames to links on follows index page twets index page and profiles index page
unit4 Lesson2 Session1 - center profile main panel
Unit4 Lesson1 Session1 move alter username function to helper file
Unit4 Lesson2 add avatar pic on the nav bar
Unit4 Lesson2 add username on the nav bar
Unit4 Lesson2 add avatar pic on profile and twets page
merge from master