Full Width Logo in in V3.0+ - Modernize

In this version you can just upload the full size(980px width) of logo in logo upload box in admin panel directly.

But just add this code

div.header-wrapper {
margin: 0px !important;
}
div.outer-social-wrapper {
position: absolute;
top: 20px;
right: 20px;
}

in custom css box in admin panel too > http://d.pr/i/Ld67

And also make sure that you change logo margin top/bottom to '0' > http://d.pr/i/pqpv

And if you see extra space between logo and main navigation, Try to add this code too.

div.logo-wrapper {
line-height: 0px; 
}
div.navigation-wrapper {
margin-top: -2px;
}