Change green used in '4.0' badge to '3.0' green

Considering the 40 badges involved for code climate (0.0 to 4.0),
4.0 having a special green would lead to only one badge having
this shade, or possibly 5 (3.5-4.0). Instead, changing 4.0 to match
3.0's green will make more sense and keep things consistent.