Code

.masthead-avatar img {
  -webkit-transition: all 0.6s ease;
  -moz-transition: all 0.6s ease;
  -o-transition: all 0.6s ease;
  -ms-transition: all 0.6s ease;
  transition: all 0.6s ease;
}
.masthead-avatar:hover img{
  border-radius: 100%;
  box-shadow:0 0 20px black;
  -webkit-transform: rotate(360deg);
  -moz-transform: rotate(360deg);
  -o-transform: rotate(360deg);
  -ms-transform: rotate(360deg);
  transform: rotate(360deg);
}